The intrigue: It's unclear whether the Senate dress code is actually an official, written policy. It appears to be more of an informal custom, enforced by the Sergeant at Arms.

This is probably the least interesting detail in this story, let alone a source of "intrigue," but it does hint at the usual lib talking point for these things, that just because [insert de facto rule of order] wasn't recorded in writing or hasn't actually existed from the beginning of time that removing it is a good thing!