I have 2 Quest 2s and both running v32 won't allow guardians to go more than what seems to be 5Mx5M.
When I try to make a 10M guardian, it seems to putter out around 5M in one direction. It just stops painting. It simply won't allow a larger space.
RESOLVED: You have to draw out from the center. I was drawing from a corner and it wasn't working. Basically, from the center of your play area, make an X 5M in each direction then fill in the box and you'll have 10M play area.