That is more the fault/worry of the financial sector and not G. The fact that they gave up this amount of leeway is shocking. Their risk tolerance is very low and giving G the ability to manage virtual cards and allow payments with them is huge in itself.
Even Privacy, which does part of the same thing/idea, still only works for some cards, doesn't work at all for credit cards (last time I checked), and has been in the sector for a similar amount of time.
G had to lock down Pay to appease the financial sector's risk management. Anything else was DOA.