My question is pretty much summed up by the title. GNOME 3.30 touts a new lock/login screen, yet Ubuntu 18.10 lacks any changes to GDM. I was just wondering if there was a way to actually SEE and USE these changes in Cosmic. Thanks in advance. THIS
Doesn't match this: 
Though I may have gotten the "mock-up" and the real login screen release confused???
Your Zamifra Honcescu is a mock-up login/lock screen (design mock-up here) targeted at gnome 3.30 that never made it into the final release. Hence the gnome 3.30 login screen still look quite the same that before and than the current ubuntu version.
May be that new design will be part of gnome 3.32 ? One never knows. And may be Ubuntu 19.04 ?
From the comments...
After looking at the two images you edited into your question, it became more obvious what you were trying to describe.
Image #1 is from 18.10, and you can tell it's different from 18.04 because of the green Sign In button.
Image #2 is not from any standard Ubuntu installation currently offered.