It has been ruled in federal court that public officials, such as Trump, may not block constituents on Twitter.
Yet Twitter continues to allow representatives in Congress to commit these crimes https://twitter.com/liz_wheeler/status/1147292766008795142?s=21
Twitter knows who these people are and which accounts as theirs, due to the verification process.
If it's someone I agree with then they're just filtering out harassment and abuse.
If it's someone I disagree with then they're cowards who can't face criticism.
My hot take: Twitter should just ban politicians from blocking people by default (they should still be able to mute people however).