is smaller than 30.9 so you would struggle to get the post into the seat tube rather than it being a loose fit .
Yes I know, although the post still seemed a squeeze , tightening well was the only option, or, so it seemed. Might try the carbon paste idea though.
My points of reference, by the way, are a 2007 Trance frame, which a mate had that was an utter bastard to get a 30.9 post into easily , and a same year, xtc hardtail, I built up for another friend, the frame came to me with a Giant branded post, marked up as 30.8 , other 30.9 posts in that were a very tight fit. Guy at one of our ( quite well respected) bike shops told me about it too.
Genuinely think that more recent models are at a ‘ proper’ 30.9 as 2008, 2012 and 2015 Giant bikes I’ve worked on were fine.
I stand to be corrected.