This series was past short, simple titles and other conventions a very long time ago.
Besides, if 2.8 Final Chapter Prologue is too much, most people will just abbreviate it. 2.8. Or Final Chapter Prologue. You're making it out to be a much bigger problem than it actually is.
I don't consider it being made out to be a much bigger problem than it is. I consider it some people just throwing out the opinions that the titles could have been better.