unity-greeter triggering mouse cursor size inconsistency on 4K display

[R]

$ lsb_release -rd
Description: Ubuntu 18.04.1 LTS
Release: 18.04

$ apt-cache policy unity-greeter
unity-greeter:
  Installed: 18.04.0+18.04.20180314.1-0ubuntu2

$ cat /etc/X11/default-display-manager
/usr/sbin/lightdm

$ echo $DESKTOP_SESSION
cinnamon

Configuration: 4k screen (3840x2160) with 1920x1080 selected in Cinnamon Display settings. Hidpi turned off.

What happens: inconsistent mouse cursor size across the screen (looks like hidpi is enabled for some areas of the screen but disabled for other areas).

This bug has more details on how this affects users (reported for XFCE but I am seeing exactly the same behavior with Cinnamon):
https://bugs.launchpad.net/ubuntu/+source/xfce4-settings/+bug/1770948

4k screen. Relevant xrandr output:
   4096x2160 24.00 23.98
   3840x2160 30.00 25.00 24.00 29.97 23.98
   1920x1080 120.00 100.00 119.88 60.00* 60.00 50.00 59.94 30.00 25.00 24.00 29.97 23.98

When switching to lightdm-gtk-greeter the issue goes away:
https://bugs.launchpad.net/ubuntu/+source/xfce4-settings/+bug/1770948/comments/11

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Bojan Jovanovic (virogenesis011)]

Anything we can do to help resolve this issue ?
I am able to replicate on my desktop, and will assist anyone who wants to fix this.

Thanks