Thanks to Messrs Funnell & Rogers for again demonstrating the utility of exploring on this list before wasting the time of those monitoring the bug list.
Indeed, for whatever reason, the "highlighting" of a selection on the Tools menu is almost imperceptible on both machines available here for test, but there is no programme bug.
By careful scrutiny, it can be seen that the selection indeed operates just as described, and one extra keystroke is a reasonable price to pay to resolve the A-A ambiguity. Having to shift from keys to mouse was a less acceptable burden.
Again, thanks for rescuing me from a blunder of my own.
trj