"Anyway, for users ..."
Ah, thats me. I am a user. I personally love terse and cryptic, i.e., minimising the number of keys I have to press. IME, multicall binaries like the OP presume some pre-existing knowledge of how to use the utilities they contain. It seems nonsensical to complain about missing documentation given the purpose of a multicall binary is to conserve space.
With BSD, the utilities in crunched binaries are generally the same ones, i.e., use the same source code, as in one in the userland. With GNU busybox, they are not, and one needs to read the source code to understand the differences.
Even if I can figure out how to use a program from reading documentation I still look at the source code before using it for the first time.