I think it would be hasty to rule out client-side mudras as implausible. There are plenty of precedents for SE designing gameplay mechanics that use the client side to improve responsiveness for players.

For those that remember version 1.0, one the big complaints was the extremely slow UI attributed to unnecessary server-side checks when opening menus. With 2.0 this was redesigned, and drastically improved.

Other examples are visible in combat too. Casting animations start instantly client-side then does the server-side check second, to help combat feel responsive. Try using a cast time spell while moving and you will still see the casting bar pop up briefly until the server recognizes your character is moving.

I might be talking out my ass, but I think it is definitely possible for mudra inputs to be changed in a way that reduces the impact of latency without making it too exploitable.