Currently, either only minutes or hours are available, which makes the use-case for it pretty small.
It's not super human readable.

It would be nice if there was a way to have it shown with a bit bigger format.
Say: Days Hours Minutes

Example:
Server online for "3 days 4 hours 45 minutes" instead of "4605 minutes"

A Solution that fit @ChakraaThePanda's needs was found with PlaceholderAPI's Server expansion with %server_uptime%
the time slowly climbs up from seconds to minutes to hours etc.

doesn't necessarily give you control over it's format, so issue will still be open