Noodles took the words right out of my mouth...The "rubbing" could be either male or female sexual/hormonal behavior. My female Cockatiel and my female Quaker (DNA tested) have both "rubbed" themselves against things, including my hand; the "rubbing" is also often accompanied by a weird, little, quiet, constant kind of "chirping", I can't really describe it accurately, but females who are masturbating or attempting to masturbate often make this little noise, it's very distinct, once you hear it/see it you won't forget it. Either way though, encouraging hormonal behavior in either sex is not good, as males can become extremely aggressive and even bite hard completely out of nowhere, like they don't even realize why they just did it (my male Green Cheek did this to me once after going underneath my couch for about 20 minutes, I couldn't find him, and when I finally did and I put a flashlight under there, he stared at me with eyes pinning, constantly chattering to himself in half English and half birdie, and then suddenly charged towards me out of nowhere and literally attached himself to my hand, to the point that I had to pry him off; he had no idea why he had done it, and he's not ever done it again or prior, it was simply hormones caused by him being in a small, dark, confined space).
Quakers are one of the only species of parrots to build "nests"; however, they aren't really "nests" in the conventional sense at all, but rather more like "Townhouse Complexes"! Seriously, if you've never seen a Quaker community nest then you should Google it, it is something to see. They make large, inter-connected, covered houses that have actual "rooms" and where different families live together in different areas. I have seen them in-person in both Brooklyn and in Delaware (Brooklyn is full of wild Quakers everywhere, there are actually different "clans" of them that have home-complexes in different areas of Brookly). I have spent a lot of time in the NYC area, especially Brooklyn, and there are different Quaker colonies in Coney Island, in Williamsburg, and then there is another colony that has it's home-complex near a church in Brooklyn, though it's escaping me now what part of Brooklyn the church is in, but there are hundreds of them there. The point is that I'm not sure how much hormonal activity is caused by their own "housing complexes" that they build, versus one Quaker being inside a little tent or something similar.
I would think about getting a DNA test done on Jack, just so that you know what his gender is, and so that you can be prepared, just in-case Jack is actually Jackie. It's always a good thing to know whether or not egg-laying is something that you're going to have to be ready for...
***And I'm so glad that you removed the "Happy Hut", for Jack's sake. I'm sorry if I came off a little aggressive about the "Hut" thing, but the fact that this company still sells these things even though they are very well aware that they have literally killed hundreds and hundreds if not thousands of pet birds just amazes me; when they started putting the warning about "Not intended for use by Conures" on the front of the packaging I was seriously enraged; like Conures are the only birds who chew on material and swallow it, or who get caught in loose threads. Andy company with a conscience and who cares about living animals more than they do money would maybe, I don't know, CHANGE THE MATERIAL!!! I know that's just crazy talk, lol...
Anyway, I tend to get very fired-up when the topic of "Happy Huts" comes-up, mostly because just calling them "Happy" Huts makes me literally nauseous. So I now call them "Death Huts", as that's exactly what they are, there isn't anything "Happy" about them. But my anger certainly was not directed at you in any way...I do get frustrated with the people who say come on here, listen to everyone and read all of the hundreds of comments written by people who have lost their beloved birds because of one of these "Huts", and then the person says something like "I appreciate all the concern by you guys, and I understand the risk I'm taking by keeping the Hut inside of my bird's cage, but I just can't take it away from him, he loves it so much. So we're just going to have to take the chance", or something like that...That's happened on here more than a few times, and I always have to restrain myself from screaming out "Well your bird won't be happy at all if it's dead, so better alive than without a Hut"....Uhg. All you can do is try I guess, can't win them all.
Bottom-line is that there are so many things that make our birds sick, accidents that happen that hurt our birds, and so many ways that our beloved family members die far before their time, that there is absolutely no reason at all for us to purposely give them a toy that we know has literally killed hundreds if not thousands of pet birds. We're supposed to be responsible for them, they totally and completely rely on us 100% for their lives and their care, so it's our responsibility to protect them, not to purposely give them things that we know may very likely hurt them or kill them...