The Travel Tripod is indeed compatible with most Arca-compatible plates and L-brackets.
How? The ball head's removable pins allow longer plates and L-brackets to lock in place.
While Arca is the closest thing there is to a standard tripod plate geometry since about 85% of professional tripods use it, we just say "most" and not "all". We've learned over the years that there can be slight geometric variance across brands.
Still, we really should say "a vast majority" because we have yet to find an Arca-compatible plate that does not work with the Travel Tripod. If you do, be sure to let us know at email@example.com!