This is my take on this.
Natural UVB does pass thorough glass.
Natural UVA is mostly filtered out.
UVA is what Fids need to process calicum.
From what I researched even the very best Full Spectrum light bulbs have to be with-in 1mt of your birds to be affective, in calcium metabilsum.
And those compact low energy bulbs have to be right up close to be any good.
That is why those with Reptiles have the lights right down on top of their pets.
But it will help with there vision.
I am with Auggies Dad and think if they are like my Fids and are in a glass environment they do get enough UVB UVA.
If they are in a internal room with no natural light they will need added lighting to remain in top condition.
If you feed pellets they will be getting some calcium from that.
But then question that they need UVA to process that.
There is some evidence or talk that your Fid could overdose, if you have Full Spectrum Lights and feed just pellets.
Natural is best every time.