in the old days (history
), with the ancient software, there was obviously a risk that once above FL300 and in a very, very shallow climb, the thrust channel "thought" you are doing a Level Flight now and so reduced the power, while the pitch channel still was engaged in CLIMB.
So easy to see what could have been the consequence on this, if you did not always check your instruments. Soon from below a very long coloured band appeared on the speed scale.
Hope this helps.
But again: History.
BTW: it never ever happened to me or to anybody I know, so I guess very rare events. Even with MSN 0025, the oldest I flew, MANAGED climb up to 390, incl shallow climb phases, not any problems.