Is there any up to date documentation for v1.17 email cron job fetching, all the ones I have read don't seem to have a bearing on this version
Because it’s the same for all recent versions.
The section on how to setup cron hasn't need to be updated in years.
How to use cron (or windows task scheduler) is dependent on the OS.
The only thing that might change for osTicket would be if the file paths changed for some reason.