No, it's that it is much easier for a bank to become a tech company than for a tech company to become a bank. The barriers to entry for becoming a tech company are merely technological. They are not trivial to surmount, but they are surmountable. By way of contrast, the barriers to entry to becoming a bank are regulatory, and nearly impossible to surmount, at least in the U.S. When was the last time you heard of a new bank being founded here?
https://monzo.com/ - not in the US, but in the UK some start ups have started overcoming the regulatory hurdles.
I doubt a startup could become a bank. But if Google wanted to start a banking subsidiary? They could probably throw whatever money it takes at the problem and get it done.
The real question is, would they care to do it?
There are many, many small banks in the US; you can just buy one that already has a license. Certainly not insurmountable.
None of those small banks are subject to the regulation that large BHC are. The potential barrier is off by orders of magnitude. The development cycle on those models is multi year. It would take a massive effort to recruit and build the quant teams alone, much less the finance, compliance, and legal personnel with the expertise.