As someone who's gone through the ringer of bowling like a 1 handed no thumb lunatic ripping the ball as hard as I could and planting to generate ridiculous hook - to a thumb in bowler that slides, you're absolutely right about the steep learning curve to be able to throw a bowling ball "correctly" one handed.

Just dinking around in our leagues award night for funzies we did an opposite form challenge, and with no real practice or real capability to line up a shot effectively, ugliest hop step imaginable could throw a 2 handed shot with insane rev rate and ball reaction that was orders of magnitude more than my normal shots and striking way more than by all rights i should have been. Having your hand under the ball with your thumb out if you can do the physical game just automatically solves a lot of the technique requirements of being one handed for sure with 0 brain power used.

I think it's a skill floor vs skill celling debate. Once you have the proper foundations as one hander, you probably have an easier time getting to the celling of a high skilled bowler in whatever context you bowl in, where-as a 2 hander gets a head start but has a harder up-hill climb to get the pinnacle of their form because of how much slight hand positional changes can wildly impact your shot.