Is it possible that the OP booked lower category room and was subsequently upgraded by the hotel after the booking was made (which then reflected on SPG.com)? I have it happen quite often the a hotel will upgrade me to a suite far in advance of arrival but will subsequently downgrade me if they are able to sell the room (which is perfectly acceptable). Obviously though if the OP is a Platinum member and was upgraded to a non-specialty suite then he should not be charged anything additional.

To OP: Was the confirmation that you printed off from the actual time of reservation or at some point after that?? I'm not familiar with this hotel and their normal room rates, but from the rate you booked would that typically be a "suite rate"?