I have one with a cracked open case that I’ve been meaning to probe out, I guess I should do that. It has been on my list to build a replacement PCB that has 32k SRAM chip and ties A15 low to override the EI memory because I’ve kinda lost patience with the whole DIN plug mess.
I just popped the lid off my original and did a little probing. Looks to me like, no, they're not, the D* signals pass straight through from one side to the other. Looks like the three '244s are entirely just addresses and control signals.
That's what I figured. If there was a bi-directional buffer such as a 74LS245 to handle the data lines, it would need an enable line derived from the address decoding inside the E.I. unit to prevent read contentions with the keyboard unit.