Well, it is not that hard to remove both. And if you want to swap or work on the tranny and engine I think it is the way to go. You can take the radiator and support right out and open up a big avenue of access.
However, I recall seeing it written that to pull a tranny and work on a clutch it is almost as easy to pull the engine and tranny to do it. That, to me, is crazy, as much as I hate tranny wrestiling, I would never consider pulling the engine to get at it.
Still, I will soon pull the B21F and its leaky tranny, out of the GT to make way for the B21FT engine and tranny. Both outgoing and incoming will be engine/tranny affairs.