I think the "Mix SSD vendors/batch numbers" is a hold over from the very early days of SSDs where a handful of people get seriously slimed by having 90%~ of their same-brand-same-batch drives in a single machine fail at once due to some SSD batch failure.

As a side effect people generally now stagger SSDs a little to avoid something similar happening (ofc if you have multi machine replication this is less of a issue, but still a total machine loss can hurt due to capacity loss or parts shortages in edge locations, etc)

I've personally not seen a synchronised SSD array happen failure for a long time, but it's hard to know how much of that is because people now plan to avoid them.

[edit]

with the exception of: https://www.engadget.com/2020-03-25-hpe-ssd-bricked-firmware...