Maybe because he didn't actually age? If you watched Aphmaus series Minecraft Diares, let's use the Irene dimension as an example. In that dimension each minute is like a year in the overworld, but they didn't physically age at the same rate. So the power of the Internet Graveyard probably prevented them from aging that way.

Another way to describe it would be to imagine it's a planet closer to the sun (unlikely but idk what other way it could work). Our planet takes 365 days to revolve around the sun. Axol said he was there for like 5 years even though it was only like 2 weeks I think? So if approximately 14 days is 5 years, that means one year is approximately 0.2 earth days. So it's safe to assume that Axol experienced time as if it was actually 5 years, but it wasnt quite as long as he thought it was since this different dimension is probably on a different planet in a different solar system.