It definitely is true, in our RHEL subscriptions we get patches that do not exist in CentOS. We also see those differences in fully patched systems where the patch versions run different binary code.
> I relied heavily on CentOS [..]
> Fact is [..]
> So this is why [..]
All those other arguments are not very relevant, they bought CentOS and then broke community trust multiple times to the point where we now have multiple re-incarnations of the CentOS concept and RHEL (or IBM) thought they could prevent that by hiding the sources used for current RHEL builds from the public by default.
Money-wise it's also not relevant because there are only two reasons you pay for support:
1. You actually need support (we never did in the past 15 years)
2. Corporate nonsense (this applies to some of our vendors)
Red Hat is fully leaning into #2 and it's just not having any real value if you don't also fit in #1.