Amelia Watson is Sydsnap, compare her voice with Watson's in any stream, and you'll see what I mean.
A regular Sydsnap video:
https://www.youtube.com/watch?v=qTYu-Swhs5k

Her voice has a slightly different tone, and she doesn't swear that much on Hololive, probably because of some agreement in the contract, but I'm 100% sure it's the same person.
Sydsnap also lives in Japan, and speaks fluent japanese.
There's also this:

Sydsnap Ara-Ara video:
https://www.youtube.com/watch?v=3H1g3DwvDxA

Watson's Ara-Ara video:
https://www.youtube.com/watch?v=-_TSIXa9sYE

The equipment she uses to record audio is clearly different, Hololive's has a lot more quality, but there is a lot of resemblance in both voices.
Have the japanese finally made me lose my fucking mind? Or does this actually make sense?