I suspect that the bpm you specify is in crotchets (quarter notes) per second.
In 2/2, you have two minims (half notes) per bar. Hence, you also have four crotchets a bar (obviously).
If the 'beat' in beats per minute was minims, then each bar would take a second, as you expected. If it's really crotchets per second, then every bar will take two seconds.
Using crotchets is technically wrong, as you would expect the bpm in a 2/2 piece to be defined in terms of minims, not crotchets. But this sort of technicality may have been overlooked by the software developers.
There may be a way to correctly specify bpm as minims per second in Logic Pro, but I could not locate it via Google. The search was hardly comprehensive, however. Hopefully a comment will prove me wrong.