I actually had a 2nd stay here in May.
I did not apply a TSU. They almost didn't upgrade me despite there being a suite available. I pointed out that it was available, and they said that it was a smoking room, and my preferences indicate a non-smoking room. I told them that I didn't care, and they gave me the suite.
I wish that there was a way to indicate that I prefer a non-smoking room if all else is equal, but my preference for a larger room or suite should take precedence. There isn't, so I just changed my smoking / non-smoking preference to "no preference".