If Remus was spying on the werewolves I imagine he took it very seriously - out of contact months at a time, never telling Sirius and James what he had been up to etc. We also know Remus is both capable and competent when he wants to be.
If then they had narrowed it down to a spy amongst the four of them, from Sirius perspective the spy is either Remus or Peter. We know Sirius thinks no one would ever suspect Peter of being the secret keeper. In the same way Sirus probably didn't think Peter was cunning enough to be the spy.
Remus wasn't suspected because he was a werewolf. He was suspected because Sirius respected him more and believed him capable of successfully spying. Especially when you combine that with Remus likely being out of contact a lot.
At least that was my reading of it?
hahaha yes i find that likely too. remus being sus bc hes competent i’d just funny. but it brings me right back to,,i don’t believe the others would think hr was the spy and not do anything about it 😭 at most, he’s just generally a little Off bc of those periods of non-contact. but i think i’m still leaning towards them not telling him for like. practicality. a combination of ‘we don’t think he’s 100% w us rn’ and ‘let’s keep this to the least possible no of people’ w a dash of ‘remus is anyway not here for it to make a big difference so no point in telling him’