I think the originator of it was on dslreports but I couldn’t find the link on mobile. I’m sure if you can search on Google you could find a secondary source for some tech blog or medium about it if that makes you feel better. There’s also a discord that covers most xgs-pon bypass methods that I could share too. They keep turning it to private at times for whatever reason.
Other links and info of you are being serious and not passive aggressive. ATT is quick with DMCA takedowns so that’s probably why the info can be fleetingly available at times but dslreports seems to be pretty reliable/resistant to them.
https://www.dslreports.com/forum/r33665048-AT-T-Fiber-XGS-PON-SFP-Modules-for-AT-T-Fiber
https://hackaday.io/project/193110-bypassing-the-bgw-320-using-an-azores-cots-ont
https://forum.netgate.com/topic/99190/att-uverse-rg-bypass-0-2-btc/440
https://simeononsecurity.com/guides/bypassing-the-bgw320-att-fiber-modem-router/
You aren’t giving us enough information to even speculate the answer. Are these Enterprise grade servers in a datacenter? Are these home made servers with consumer or low grade hardware you’re calling servers? Are they in the same datacenter or do they go out to the Internet? What exists between the hops on the network? Is the latency consistent? What is the quality of both sides of the connection? Fiber? Wi-Fi? Mobile? Satellite?
Does it drop too nothing or just settle into a constant slower speed? What have you tried to trouble shoot? Is it only rsync or do other tests between the hosts show the same behavior?
Give us more and you might get some help. If these hosts are Linux I would start with iperf to do a more scientific test. And report to us some more info.