Capella, the ultra-luxury brand I most frequent, seems to price things deliberately so they remain below 100% occupancy even at peak times, which creates capacity at least for standard rooms to offer early check in and late check out on a frequent basis. Clearly this doesn’t work if you want a specific higher category, where they will sell all the rooms of that type.

Maybe that’s what they meant rather than every room is kept empty between guests which I agree would be madness?