YouTube didn't say he didn't need to. Show me in the terms of service where it says that as long as they follow specific guidelines that they don't reserve the right to flag or remove content.
You accidentally only got the first third of the rule?
> You can turn on ads for this content:
> Abbreviated, censored, or light profanity (like “hell” or “damn”) in the title, thumbnail, or video. Moderate profanity (like “shit” or “bitch”) used in the video. Infrequent usage of strong profanity (like the "f-word”) after the opening or up to twice in approx. the first 30 seconds of the video; or strong profanity in a music video.
There was one single burst of fucks. That's infrequent use of strong profanity.
The next category up, which is still the intermediate category for advertiser friendliness, is "Focal usage of strong profanity throughout a video (e.g. mentioned in every sentence)."
As far as possible standards go, he was very far inside the relevant rule.
I don't know why you would interpret "said he didn't need to" as "legally bound themselves to inaction in such a case".