Thiem was playing with Head, one day he went into a store, demo’ed a 16x19 PureStrike, loved it so much called Babolat for a sponsorship. That’s the official story anyway and if real, Babolat has struck gold to land one of the best player outside the big three.
He played a modified PS 18x20 in the sense that he has a modified grip based on the Head shape and of course the extra lead visible in pictures.
He didn’t switch to the 2nd generation as the grooves (I don’t remember how Babolat calls them) from the 1st gen were very visible in pictures. The grommets were also first gen. It was just a pj over the 1st generation PureStrike, that’s a known fact.
Then it seems early this year Thiem moved to the 3rd generation. Stringers at tournaments can sometimes tell if the frame feel lile the retail version. It’s hard of course to tell of the layup is the same but it’s reasonable to think that if Thiem was involved in the development of the frame that he is using a retail version. Now, that doesn’t mean he’s using a retail frame that you can pick at any store as his frame are certainly hand picked with his desired specs, then the grip modified, any needed weight added and custom graphics added (I don’t know if he has any).
So in the end, no he is not playing with a store frame, but in his case it’s pretty close. Young players tend to play close to retail frames. Older players that used to play with frames that are discontinued will have access to these older frames. The players switching from other companies can sometimes ask for frames that play similar to their former brand and will have access to “pro stock” frames that are built for customization. Players don’t just happen to start playing with new magical frame once they reach the top 100. Most here know that, but some still believe that once you get there (Top100) you have to forget all the practice time of your last 20 years playing tennis and move to the secret prostock frames.
Regarding the 27,25in frame that’s the fitst time I’m reading about this. Maybe he changed to an extended frame with this new version. Some stringer will be able to confirm that. However, even if Thiem is known to try different strings throughout the year, I highly doubt he changed his racquet length mid-season.