Personal records don't compare you to other people, it is just a listing of your personal best. Are you proposing that the existing system be updated to display your historical personal records? i.e., your 5K times from when you were was 20-25, 26-29, 30-35, ...?
If sole purpose is to keeping up PB's than why put them in AG's?
The AG's are meant to put yr achievement in perspective. Not that it is done right cause 10 years groups above 45 or 50 are too big! 5 years is minimal, as used in the competitive world. (not everybody is 'amateur'!!!)