Yes, I've cancelled points bookings in Manchester, Shanghai, and Luxembourg, as early as 3 years ago and as recently as last month.

As far as I know, that's how it always is for reward nights.

Points and cash is not the same. That's a cash rate with a discount in exchange for some points, so it always takes on the properties of the cash rate, not a reward night.

When I've cancelled reward nights, the points reappear within a few minutes.