If you can pick up on the patterns of an unfamiliar language and/or codebase and make your code look like it fits in, you're probably good at both reading and writing code, and working with a team.

I can't speak for the parent commenter, but by "patterns" I am referring to multiple layers:

Detail -- Indentation, spacing, line length, naming convention, placement of braces and parentheses.

Flow -- pacing, grouping of blocks of code, levels of nesting, when and where to break up functions into spaced blocks or helper methods.

Architecture -- class boundaries, interfaces, cross-file organization.

There are higher layers but I haven't named them yet in mind and they aren't as well tested by this kind of interview.