FAQ gnmap
From SecWiki
Why is X missing from the Grepable output?
Greppable output (-oG) is deprecated. It is not very extensible, so it can only display output from features that were in use the last time it was updated. Notably, it is missing output about traceroute and NSE scripts.
The solution is to use the XML output (-oX), which contains all the results of any scan in a machine-readable format.