A baffle in the bottom?! Really?
Unless there's an air vent in the top, I don't see how the tank would fill on immersion, but from your description it sounds as if it's designed for daylight processing in traditional 5 gallon hanger tanks (which would normally be used in the dark). You'd agitate by lifting the whole unit clear of the liquid, in any case, letting it drain for a few seconds (preferably lowering alternate sides on alternate agitations), then lowering it into the soup again.
If you do a lot of 4x5 and don't like standing in the dark while you process multiple stacks of 6-8 films, maximum, and can get the hang of loading hangers without scratching film (something which, I've read, even commercial lab techs don't always manage), this could be a very useful item!