I think for the most part, people are more concerned with 1 Corinthians than with 2 Corinthians. There are also only 18 questions with this tag and only two of them are about the second epistle 1 2. None of them appear to be about the church or the people of that area and time specifically.
So I don't think changing the tag serves a real or useful purpose today.
That said, I still think it should be done. If I were doing a study on 2 Cor. I don't want my search to include wading through all the 1 Cor. posts if it doesn't have to. Further, I may actually want to ask a question about the people and church of that time. The current tag excerpt excludes that use.
So, yes, they should be separated into:
- corinthians where the excerpt says "the people and church of Corinth. Use 1-corinthians and 2-corinthians for the epistles."
- church-in-corinth Alternative option to the above tag. It's a little more descriptive, but it will show in all tag searches for "church", which may or may not be desirable.