I used to have this game. Just don't remember the wood there. ...I can't be certain if it was there or not, it doesn't look familiar. Maybe it is there to shore up a failing cabinet joint? Why does it matter...Is there some problem with it?

Does it look like anything was ever mounted to it?

Might just be for support. The cabinets are not that sturdy despite being quite heavy.

My Eight Ball Champ did not have the extra wood in it.

Escape from the lost world is in the banana shaped cabinet. It is pretty funky.

Now I remember. There was something I read specific about these "banana cabinets" with the weird shape.....something about using a certain type of lift where you would take a piece of wood and shim or level the weird shaped banana cabinet to make it work. Maybe that is wood for that?

That's it!
Checking the manual, that's the "dolly assist stilt assembly" that gets screwed to the bottom rear of the cabinet during transport to make it level. Missing from mine and wasn't quite sure what it would look like. Picture on page 1-5 of the manual shows this piece of wood installed.

Man, that's CHEEZY!
Having read the manual but not seen the piece, I thought it was a wedge shaped assembly. It's just a 1x4 with a couple metal pieces on it.
Bally sure is building things cheap these days.