I know this is probably beating a dead horse but I looked into it briefly to see if the affliction was a curse or a disease and found a lot of information on lycanthropes and it would mean a lot if it was maybe looked at again by staff. I know it would be a lot of work to take another look at lycanthropy, so I tried to gather all the sources I could find to help out so you don't have to spend time digging. I couldn't find anything that said "human only" except what I believe is a typo in Races of Faerun (noted below) and weresharks (which are specified to be human kind of? It's confusing). I only used FR 3e and 3.5e sources for lore accuracy and I spoilered the snippets from each source so that it's not spammed.
My suggestion is that lycanthropy is changed from human and giant only to any humanoid
Forgotten Realms Campaign Setting (p 277-278):
Monsters of Faerun (p 91-93):
Lords of Darkness (p 131, 168):
Player's Guide to Faerun (p 6):
Races of Faerun (p 142-147): (edited for accuracy)
Serpent Kingdoms (p69-70):**Mostly references human as their humanoid form but it does say they're humanoids or giants
Silver Marches (p 80, 128-129):
Champions of Ruin (p 79):
**This is based on Eldreth Veluuthra membership only being available to elves
I mean, at the very least you'd have to exclude elves from humanoid since lycanthropy is known to kill them upon contracting and they cannot be born as such. Also, giants do not count as humanoids so their special mention is necessary as well

Do you have a source for that by chance? Several elves are listed as lycanthropes, not Lythari in multiple sources
I mean, I only read about lythari as elven lycans, and admins ruled that elves cannot be lycans. Figure it comes from a source I cannot find rn, but the rulebooks about lycanthropes I can find do not specifically mention they are included as well.
Edit: I was wrong about the typo, it says lycanthropes of other races are not impossible. I thought it said not possible, but they just used a double negative