> is just a trivial table lookup

So just an inch to the left goalpost of the True Scotsman's "filesystem" definition.

> make it very hard to write a single FAL which works well with all flash chips

Right? So the last thing you want is to foist that logic into filesystems. The layered separation is good.

Hence, someone upthread wrote: A flash adaptation layer solves the following problem: I have M filesystems, that I'd like to use on any one of N different flash technologies. I don't want to complicate each M filesystem with support for N flashes.