In the FAQ at https://www.gnupg.org/faq/gnupg-faq.html#generate_inline_signature, it says:
An inline signature wraps a textual header and footer around the text to be signed, leaving the text readable without running GnuPG. This doesn’t conceal the text at all and therefore provides no secrecy, but if someone edits the text GnuPG will report that the signature is bad.
It should be updated to make clear this should be avoided if possible, and detached signatures are preferable (T7902 etc).