S0 Only devices that can join with no security can join just fine, but only as none. (S-none) S0. You can't join S0 Only devices as S0. S-None
Devices that are S0 Only AND are barrier devices, which means they MUST join securely, are impossible easy to join, period. If they join as S-none then their barrier code prevents them from working.
No.. Hubitat can safely be left out of this. It's pure SiLabs insistence that to remain certified, that S0 devices must 'bootstrap' to S2. The code that's out on the Zwave radio chip is a SiLabs image.
EDIT to correct per @jtp10181 and @bertabcd1234