Hmm… 
No, it’s not new, but there’s a caveat. We respond with a populated array of tag_ids when getting an individual contact (/contacts/{id}). However, when getting a list of contacts (/contacts) we respond with an unpopulated list of tag_ids:
I wish I could say we goofed but it looks like our over all behavior is unchanged except for the message. We’ve been rejecting create/update requests with tag_ids for well over two years.
@Terry_Kim I’m stumped as to why you might still be having issues. 