This valve stem seal replacement job on the 2.5T isn’t easy even with the special tools designed to eliminate head removal. You can go through the repair steps in the TSB and see how complicated the job is. The TSB also stated that:
“This repair can only be performed by Senior and Master Technicians.”
which also indicates the level of difficulty for the job.
Although I also hate to let a dealer perform such job to my engine. But if I had a 2021 2.5T I won’t hesitate to have this job done right now, as for one I have no choice but to let the Mazda dealer replace these inferior exhaust valve stem seals which for sure will fail in the future. Secondly those Master Tech at Mazda dealers should have enough experience now for this job and chances of screwing things up should be minimum.