Hmm, their developers seem to imply otherwise:
> TS.ChrisR - TeamSpeak Staff - 30d
> We use the Matrix protocol only for the messenger part.
https://community.teamspeak.com/t/beta-signup/13749/50
Other mentions of it here:
https://community.teamspeak.com/t/teamspeak-development-stat...
https://community.teamspeak.com/t/teamspeak-development-stat...
Matrix themselves talked about it: https://matrix.org/blog/2020/10/09/this-week-in-matrix-2020-...