I have done a bit of reading up on Mazda's yearly changes on the Skyactiv 2.5T engine and from what I've found it seems that Mazda made somewhat of a revision to the engine for the 2020+ model years, they added a "Engine Harmonics Enhancer" (this is pertaining to the CX-5, but I would imagine it's across the whole 2.5T range) as well as upgrading it to a ULEV70 engine. They introduced enhanced (probably more performance oriented tuning) for the Mazda3 Turbo as well.. Seems like they are doing constant revisions which is a good sign that they would of made changes to the engine to fix these problems, also the torque increase, change to the new "A" block and head part numbers seems to support that theory.
I just did my '21 CX-5's first service yesterday and while I was under it I searched all over the engine block and looking for any part numbers I could use for research, so far the only thing one part number led me too was eBay listing for a used engine block, everything else seems to be internal Mazda codes or serial numbers. My plan is to keep a close eye on my CX-5 for this coolant leak within the warranty period and make sure to document it if it does happen, I'm glad Mazda went to unlimited mileage warranty in Canada so I have 5 years where I can monitor this before I need to worry. So far nothing else I've come across seems to suggest that this is a widespread issue.
I have also contacted a Mazda tech and he had nothing negative to say about the turbo engines, he has not seen any of these failures at his dealership. So far it seems to be isolated to a few early production engines and judging by the comments in other threads saying that Mazda service personnel have only seen this on 2016 CX-9's makes this seem to stand true. I know there was someone who reported this issue with a 2017 CX-9 but to my knowledge nothing newer than that, if you know anything about how production runs and batches work I'm not at all surprised if some 2017's and maybe even 18's end up with these issues once they get up into the higher mileage range and Mazda will probably just keep doing what they're currently doing and just replace them as the failures come up as long as your in the warranty period. I highly doubt Mazda would let this issue slide internally, for one they can't afford it being a smaller, low production company compared to their competitors. They're putting this engine into pretty much every Mazda now save for the tiny CX-3 and MX-5's so I would imagine it would be a costly oversight. I still plan on shooting an email to my Mazda Parts Advisor to see if he's willing to look up anymore info for me. Hopefully this helps get some more understanding of this.. I'm very curious myself about this issue.