The Transporter Room in LTBYLB is different to every other one seen, in that the wall adjacent to the door (on your right as you enter) sweeps forward at a very sharp angle, instead of the usual 90 degrees. Add to that that we only see the front two pads, and I'd suggest that what we are seeing is a smaller, auxiliary room instead of the usual one(s).
Perhaps this is the Transporter Room that is used when saucer separation occurs? Those impulse engines are not in the same league as M/AM reactors, a small T-Room is probably all they can handle!