Some blues are reversible, and some aren’t. Some of them do a statistical rearrangement of the data in the area being blurred that’s effectively reversible.

Think shredding a document. It’s a pain and it might take a minute, but it’s feasible to get the original document back, give or take some overlapping edges and tape.

Other blurs combine, distort, and alter the image contents such that there’s nothing there to recombine to get the original.

A motion blur or the typical “fuzzy” blur can be directly reversed for the former, and statistical techniques and AI tools can be used on the later to reconstruct, because the original data is still there, or there enough that you can make guesses based on what’s there and context.
Pixelating the area does a better job because it actually deletes information as opposed to just smearing it around, but tools can still pick out lines and shapes well enough to make informed guesses.

Some blurs however create a random noise over the area being blurred, which is then tweaked to fit the context of whatever was being blurred.

Something like that is impossible to reverse because the information simply is not there.
It’s like using generative AI to “recover” data cropped from an image. At that point it’s no longer recovery, but creation of possible data that would fit there.

The tools aren’t magical, they’re still ultimately bound by the rules of information storage.