"If the element is mutable, its value SHOULD (emphasis mine) be editable by the user. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the element's value."
https://html.spec.whatwg.org/multipage/input.html
So, according to this spec, the UA is allowed to make an input field type=text non-editable if it so chooses.
Would you argue that this is another place where Chrome would be allowed to act in a manner differently than expected, because "SHOULD" was used?