Yeah, you understand the code - we all do. But it doesn't tell you anything about the context the code runs in. And its context doesn't tell you about its context either.
The function names do. Honestly, this is very, very simple code. Most of the code in a kernel is nothing more than book keeping or glue connecting things. This is glue.
There are cues here that are consistent with conventions in the Linux kernel. For example the sys prefix on the function name tells you everything you need to know about "the context the code runs in" - it's a syscall. "compat" gives you a hint that it's a wrapper for another ABI.
Sparse code is not necessarily self-explaining.