One other reason they may have chosen to reuse the same angle for the Ackbar reaction could be some version of the ‘180 degree’ rule. As in, showing the underside of the SSD may have been disorienting to viewers.
There is also the consideration that we know that Ackbar is viewing the SSD from that angle in a previous shot. To show the underside of the ship would require it to twist or flip over somehow, rather than simply falling down out of frame like it does in the film.
That’s a very good point; I forgot about the previous establishing shot of Ackbar’s view, which is dated August 13, 1982.