Unfortunately, I've never heard Blakey play live, but from recordings, I think Blakey's playing from the 80s onward occasionally featured off-rhythm or unstable moments. If it's a decline in hearing, that makes sense.

and in 60 years, historians may read this post and speculate whether it was one of the triggers for the miserable documentation of discographical data in the 2030s  but, yes, the hobby historian in me also only comes out for the old stuff, it's what hobby historians do

For contemporary music, it does not bother me. When artists were playing and even revording  on a daily or weekly basis, it made sense to refer to sessions by exact dates - today, alas, it is not really relevant.

As Bertrand said. I like Junior Cook's playing a lot. Would love to get some reviews of this book before laying out the money.