`std::ascii::escape_default` unexpectedly prints in LowerHex even though documentation specifies UpperHex

I tried this code:

println!("{}", std::ascii::escape_default(0xFF));

As per the documentation for std::ascii::escape_default:

Any other chars are given hex escapes of the form \xNN.

I expected it to print "\xFF", but instead it printed "\xff".
See Playground

Meta

rustc --version --verbose:

1.93.0

same issue in beta and nightly channels obviously.

I couldn't find whether this has been reported previously. Can someone confirm whether this is a bug or outdated documentation? If so, I will prepare a PR to fix it.

Start with std::ascii::escape_default and the linked standard-library documentation, then reproduce the output with the provided snippet or Playground. Determine whether the implementation or documentation defines the intended hex casing; done means the behavior and documentation agree, with an appropriate regression check.