For the software industry ( for other industries or use cases that might certainly be different) I think it is. It’s just one possible indicator but an indicator it is.

If I come across or meet a new person from this industry and that person has a Twitter account I routinely check the follower count.

A somewhat large number says to me: “Many people seem to think that person has something relevant to say.”

More realistically, a somewhat large number (>1000) says to me "this person spends time and energy on self-promotion". Some of the smartest people I know have Twitter accounts with just 100-300 followers because they don't aggressively blog or anything.