As a legacy Marriott guy, I'm not familiar with how legacy SPG properties handled the SNA pool but its my impression that it was all over the place and depended on the hotel. That's my impression now as well. That being said, I've requested to use SNA's once and the SNA went through and I had a 1250 square foot one bedroom suite overlooking the Mediterranean ... so no complaints!

Additionally, in general, before the Bonvoy integration, legacy Marriott properties in APAC would routinely upgrade me to nice suites before arrival. Looks like Taiwan may not have been covered by that program though so not sure how they handle it.