Different anon here - They looked more like 'JE' to me towards the beginning, more like 'JG' for awhile but I had already figured out whose initials they were. So I think it is the handwriting, like maybe writing in cramped quarters (the cockpit?).
I bet this all links in with Weinstein too, and was probably installed / made possible by WJC. Was just looking at Weinstein complaint again – can start on p.26 if want a refresher of their game:
https://www.scribd.com/document/364467660/2017-11-15-Weinstein-Complaint