He said that the banning process was NOT automated. When there's a report of hate a member of staff looks at the tweet an decides if it contravenes their policy.
GDPR also provides for a person in such a situation (who has been banned) to relieve a clear explanation of why and how this was done.
I would be very interested to hear how a statement of biological fact, such as ‘humans cannot change sex’ can be justified as hate speech. I’d suggest anyone banned get in contact with twitter and ask for a full explanation under GDPR, reminding them that a truthful and scientifically accurate statement is not hate speech and that ‘violates policy’ is not a sufficient response under GDPR.