Perhaps the point is that an Aft Cargo Bay warning isn't sufficient reason to risk aborting the take-off (which presumably carries it's own risks). So the warning alarm would go off & the pilots would abort because they were used to having such minor alarms being disabled about 80knots on their previous aircraft, therefore any alarm at speeds > 80 knots but < V1 is would previously have been cause to abort but on the new aircraft this was no longer the case.

Makes sense? (Although personally I'd have thought that an open cargo bay door would be reason enough to abort a take-off - so that bit doesn't make sense to me at all.)