Well, of course you can test this issue on real hardware. But you might as well have believed their statement in the ReadMe file
, page 19 of 22, in the first place already
And in the meantime, this has been added to the "Installation description" text info for that download, too. Doesn't appear to be "important", though (like the Auto Deploy restriction information for Japanese customers)
Seems we'll have to wait for a fix to the underlying problem...
I assume (well, hope) that this fix will be announced in an upcoming patch release soon.
Until then, you either must stick to your older ESXi, or (at least temporarily) install your ESXi 6.5 to a different boot medium.