Can somebody tell me why this is anal and not ambigous. I got 5 downvotes at the post itself for asking that question :´( ´:D

The tagger may have been following the tags on the FA post, but I agree with you. I would've probably tagged it as vaginal myself, going by tag what you see. Adding to the confusion, it's also tagged cum_in_pussy.

I wouldn't mind 'ambiguous penetration', but it seems a little too far back for it to be vaginal.