scubaccr

As discussed before regards Amb/RA t+c's the described benefit is "upgraded during checkin".
No requirement at all on an IC hotel to block rooms and be unable to sell them, especially if you booked say 300+ days ahead.

Maybe IC-PLG did not have Royal, Ambassador Suites added as htel specific exclusion is because before the recent Amb/RA t+c block rewrites, a general exclusion covered this saying something along lines ... Royal Suites and Presidential Suites are excluded from upgrades

Before one of the more recent rewrites, certainly a rewrite after the Sep2016 rewrite, the catchall exclusion stating regards upgrades "excluded for Royal and Presidential Suites" which previously appeared has been seemingly lost... I'd say unintentonally lost by the rewrite edits.
Pushing an IC pre-arrival for such a suite upgrade will draw attention to that loss and probably lead to hotel telling IHG to add the global exclusion back.

I just checked both the Intercontinental and IHG versions of ambassador t+c's, the original "Royal+Presidential exclusion" text is missing from both. Funnily there is a final bullet exclusion regards Residence properties (tI am hinking like Saigin IC residences) but Presidential not metioned so not replacing the misssed of exclusion
o All InterContinental Residence Suites properties: Ambassador and Royal Ambassador room upgrades are not applicable. All other benefits apply.

IC-PLG has I think 3 Royal Suites, 3 Ambassador suites, with +2cat upgrade now for RAs, even if not sold direct for paid bookings, if four RAs book 2cats below royal suite then not all four RAs can be upgraded to a royal suite

I'd be extremely wary of pushing IC-PLG pre-arrival to guarantee +2cat on RA upgrade to Royal, as then IC-PLG may forced to react by simply adding these great rooms to the t+c exclusion list nder each hotels name, which is not in our interest