You're skipping half the recommendation though:
> Array indexing must be properly tested, or the get method should be used to return an Option.
emphasis mine
> Also, in rust if we don't want to panic we need to never use array indexing and never use integer division, just to start.
I mean, that's literally the block above the one you quote:
> Common patterns that can cause panics are:
> * using unwrap or expect,
> * using assert,
> * an unchecked access to an array,
> * integer overflow (in debug mode),
> * division by zero,
> * large allocations,
> * string formatting using format!.
>> Rule LANG-NOPANIC
>> Functions or instructions that can cause the code to panic at runtime must not be used.
The bit you quote is really a additional reminder that array indexing is not panic-safe.