I believe the left consumes more social media political content (much like they do with tv and newspapers) so this shouldn't be surprising.  There isn't a technical case why bsky should be better.

Ultimately I don't think we'll know until the 2026 midterms whether isolating themselves in a hugbox helps or hurts them politically.  If they're able to draw the centrists in and control narrative then bsky wins.  if not, it probably dies on a long enough timeline.