The whole point of a powerbank is to be a spare power source, sometimes even used for emergencies. Why give it any other functions that drain it's batteries?
Especially since Your phone can do those things better and you have it on you (otherwise why carry a powerbank at all)?
I feel like some companies are desperately trying anything to stand out of the crowd, a voice-recording power bank defeats the purpose of the primary role (voice recording uses power from the power bank, which should be reserved to power your phone, which can already do voice recording...).
It's more interesting to wonder how they came up with this idea, and especially what sort of flawed mental process led to approve this as a viable product at all.