This is what I was thinking too. Effectively with the generally good value suite upgrade for points programme via SPG, the hotel is substituting a suite upgrade for some additional points for any member prepared to pay for additional capacity for free upgrades for Plats. I have never noticed this as an issue and increasingly pay for a suite or use SPG points to get a suite when I really want one.

I have so rarely had a suite upgrade at Hilton properties (I can think of only 3 upgrades like this ever as a Diamond with Hilton) that it isn't even an "unwritten rule" it is a rare exception to the standard Exec Floor upgrade that a Diamond is entitled to.

The HH approach to upgrades appears rather different from SPG, but then the points for upgrade element of the SPG programme throws up some quirks too (like almost 100k points at say the Westin Whistler to secure the most marginal of upgrades). I am really keen to understand the level at which these upgrades are pitched. I fear you are probably right about this being higher than Starwood given that upgrades can be booked far in advance (rather than only 5 days out under SPG).

Whole properties could quickly become overrun with points upgraders at the expense of paying guests. I would really like to understand how this will play at resorts like the Conrad Rangali where upgrades to the better villas are rather expensive.