This is what caused several airlines eg CO/DL to hold back upgrades close to departure. If the upgrade wasn't confirmed days in advance, it wasn't happening, and seats would go out empty up front.

There are better ways to combat this, and those airlines eventually made positive moves, as they truly angered customers who had paid higher fares in order to have the CHANCE of an upgrade -- the seat was available -- but they didn't get it.

That said, the 'technique' descried above is hardly a strong one for tipping the scales in favor of an upgrade towards a specific member. You may block out several suites, you could even prevent a few from being sold that otherwise would be. But hotels where someone would want to do this are likely to get MANY Platinums, and you may just be making the room available for someone else or several someone elses.

Moreover, what makes anyone think they're preventing a room from being sold? Making these reservations only helps if all the suites would have otherwise been sold. But if there were going to be 5 empty suites available for upgrade anyway, all you've done is put the rooms back into the upgrade pool when you cancel, and they're allocated however the hotel chooses to allocate them.

Seriously, this is actually not that likely to make upgrades that much more likely for anyone, let alone the one perpetrating the 'technique'.