So as an experiment, to rule out BIOS, EFI, and any hardware on this machine, I installed windows 10 in a dual boot configuration. The external drive is fine, showing 2.7 TB and is fully accessible when booting in Windows 10, but in windows 11 it's inaccessible with only 746 GB recognized in Storage Manager (not usable / accessible)
Sounds like drivers (Chipset / USB,... Or...?) is the culprit. I guess the Z440 is not supported by Windows 11, so it's a chance I took.. so be warned folks.. if anyone finds a solution, please share.