if you join a separate server it actually loads that servers m.dts in your avatar menu
what i mean is that the hats are bots, not a modified m.dts. In order for the hat models to load, you'd need to either join a server that executes the dts files or host your own.
The m.dts is the only model that is loaded, since it's in the base/data/shapes folder. The bot hats, however, will only be loaded once the add-on is executed, which can only happen when creating a server