I don't know why it works that way, but hey, at least it works!
I noticed it as well! You can also use the URL in the Address Bar, although sometimes that contains more "gunk" that may not be required, and I don't know if it would mess up the embedding feature or not. Haven't tried it....
It'll probably be an 'on-going' issue for years to come... every time the forum software is upgraded. Happened on another forum with pictures. With the way you could "attach" an uploaded photo into the post, it would show up in the post rather than uploaded and then having to click the image to enlarge... well, forum was updated, and that feature was lost. All images uploaded in that manner were 'dead'. Some years later, the forum was updated yet again, and the images worked! However, all images that were uploaded between the times it worked were then dead. A major pain...
Anyway, glad it fixes the issue!