Fansub encoders usually use a constant rate factor (constant quality) and not a constant bitrate. This causes file sizes to vary for the reasons explained by Leggy.
Streaming services (CrunchyRoll, Hulu, Daisuki, etc. — files ripped by HorribleSubs) on the other hand use a constant bitrate, leading to very uniform file sizes.
You could always use Hiryuu's version until FFF's is released. I did have some weird subtitle issues in it though (the subs were inconsistent until after the opening).
Remember that all link contributions will be re-uploaded as best as possible. Keep in mind that some will not be available because they can no longer be found. So I will see if they are still sold digitally. I hope they are available.
I don't know if it's because of the times when users are more active. But if you have the possibility to download a torrent file, at least keep it on your PC for some time so that it can be shared, or at least upload it to a cloud storage service like MEGA or MediaFire, etc.
Any requests, send me a message about anime music. I will do my best to help you since I also like anime music. Remember to download the complete torrent and at least share the files for a long time or post them here and upload them to a cloud drive for preservation.