I'm at fault here, as I first created that tag. However, I agree with @terdon's answer on another question that, separate tags for separate versions of a tool aren't helpful unless there was a big change and expertise between the 2 versions if completely different.

Should apache2.4 be a synonym of apache2 in that case?

I have created a synonym suggestion for the tags as the Rinzwind's seems to be the preferred opinion (I assume I did it correctly).