Hypothetical: If you were to book a 5-night stay now, but then in the future decide you only need 4 nights, can you amend that reservation and remove one night even if since the original booking that time period is now 'sold out'?
Yes. Any change to a reservation results in holding points. Even if one wants to swap out points.
For example, say I had to cancel my DDs upcoming trip. I’d have banked points. If I tried to swap those into my late October trip..which just hit 30 days, my freed up points would be holding as well.
Basically, the only change within 31 days that you don’t end up with holding is adding days or booking a more expensive room since the holding points are used in the modification