It is guaranteed, but sadly, IHG introduced this 10,000 points "compensation" loop hole a few years back into the AMB T&Cs.

Some properties are using that as a way to sell higher category rooms / suites (if not on excluded suites list) till last day and then only on day of arrival decide whether to upgrade the 1 category or provide the 10k points instead.

Other properties do process the upgrades within days of receiving the booking to manage their room inventory accordingly. That way they only need to "activate" the 10k compensation when to be upgraded room suite category is already sold out or so.

Both approaches are in line with the T&Cs, so in the end depending on property. If you would not stay at the hotel if the upgrade is not confirmed by hotel prior to booking cancellation deadline, then all you can do is make this clear to the hotel and request if they would consider confirming the room upgrade upfront.

However, be prepared that they may still say no and risk you cancelling (especially if rates have gone up since you booked) and ensure you have another fallback option booked / locked in. YMMV.