You have a known working regulator, with known working gas, and if the reg gets grabbed out of your mouth, then no problem. If you have someone with a communicable disease you deal with it on a case by case basis.
This is me. 1) I test both of my regulators each dive. (In all honesty, I can't claim that this is a direct safety step I take, but rather a desire to make sure that they are both still tuned and running well since I am the reg tech and I want to track this info. It is indirectly safety but it'd be misleading to claim that is my primary thinking when I do it.) Usually after leaving the surface. and then again if we go past another atmosphere of pressure give or take a couple of feet. If I have a flaky backup, the dive should have been called well before we got to any OOA situation. 2) What are the statistics on me having an OOA buddy and a faulty backup second versus a possible communicative disease issue? Both are pretty dang low. But I have the luxury of a new-ish diving family that even after 60+ dives (our least dove member) we all check our SPGs more often than is probably needed. so 3) I would either have a buddy with a catastrophic low pressure leak or a random stranger that found me underwater combined with a backup second that went bad mid-dive. That is either two independent hardware failures on the same dive or a random stranger that finds me in their OOA time while I have a communicable disease. I'm keeping my primary donate setup. My wife knows to go for it.
I can't say for certainty that I would avoid this resort, but it might have to have some compelling reasons for me to not look elsewhere.
A bit long winded this AM. apologies.