Nitter instances are a scarce resource provided by the community, and they want to make sure they're available for actual users and not bogged down by AI scrapers looping through URLs. Not sure why that would be amusing particularly since Anubis doesn't require any kind of account...

Anubis at low difficulty isn't a roadblock to humans and it doesn't affect anonymity at all. Seems reasonable to me. Their mission isn't to help with mass requests.