The use their dialect of Lua. Luau, stuck on 5.1 (correct me if I am wrong) like LuaJit for performance reasons.
It is gradually typed, so no need to use Teal.
> Luau, stuck on 5.1 (correct me if I am wrong) like LuaJit for performance reasons.
It's not just for performance reasons, and they don't exactly have no features from newer versions. Take a look at the compatibility tables: https://luau.org/compatibility
Mainly on 5.1
Actually I love luau
the stuck was not expressed as negative, sorry If I gave the wrong impression.