FWIW, a friend of mine works at a hotel in Taipei. They had a guest checking in a few weeks back who informed them that he's arriving from Wuhan. Per Taiwanese government regulations, he was forced to quarantine and stay in his room for 14 nights. He was aware of it and expected it. They forced him to pay (he used points IIRC), but cut him a deal of sorts on food (he was also an elite member, but obviously couldn't avail of lounge benefits, so they gave him room service breakfast and a light dinner for free). Probably a fair arrangement since it was "by choice," although TBH these hotels have ridiculously low occupancy, but are not lowering their rates, so there is an argument to be made that it's unethical to charge full rates to quarantined guests.

Now, if an entire hotel went into lockdown, I don't know if the people who are stuck there due to no fault of their own should pay the full rate. I suspect the hotel would certainly try to charge them.