I suspect USB PD doesn't make much sense on small powerbanks. With 5V and 2 Amps you're already pulling 10 Watts. At 10 Ah with one cell you only have 30 usable Wh's.
If you go up to USB PD profile 2 with 18 Watts or profile 3 with 35 Watts that's on a 5 Ah bank such a big power drain that I don't think there is much usable capacity left due to all the losses and internal resistance.