RocksDB supports hashing at multiple levels (key, value, files) because Meta also realized the importance of integrity. It also supports verifying them in bulk.
Presumably filesystems built over rocksdb also support this.
The recent Ukraine war shows that soldiers lifes are cheap - according to commanders.
So many soldiers on both sides died because of really dumb commander decisions, missing kit, political needs, that worrying about CPU errors is truly way way down the list.
It would be easy for competition to reverse engineer the physical layout.
I think it's "secret" because nobody really cares.
Do you care for example how the CPU maps the linear memory space across physical RAM sticks and chips? I recently discovered that there multiple alternatives and BIOS settings which give you some control over this.
People learn over time that complex web apps work badly in Firefox, because developers mostly test in Chrome.
So they don't even bother trying it in Firefox.