False endorsement is definitely annoying, yes. It's also illegal.
Would changing that text actually be enough? On its face it would still appear to other users as if the people Musk "sponsored" are real subscribers. How many people are going to (know to) click through to those checkmarked users' profiles, click on the blue checkmarks, and discover that bit of information? Especially if the number of sponsored users are a handful out of tens of thousands checkmarked users, meaning that even a person who was in the know would probably be disincentivized from checking every checkmark they saw.