[HELP/opinions] What does TMOBILE_DEMOUNIT mean?

So in my ever on going quest for a discount, I found a wireless shop that had an LG G4 H811 Tmobile variant available for sale. After checking the device out, going through the typical hardware tests and such, I notice it has small indentations on each side mid center of the bezel, but I wasn't going to be picky. I did ask the person if the device had had it's screen repaired or if she had any idea what caused it. She replied, the previous owner might have dropped it? Afterwards I thought it was probably a GPS mount, (but after searching for TMOBILE_DEMOUNIT, which I read as de-mount-it for some reason, google suggested TMOBILE DEMO UNIT).

Does anyone know if this device will work as a regular phone? I did put in my sim, but it's not sim unlocked. I also tried with an inactive account tmobile sim and it did dial and connect me to tmobile customer service. It appears to have been a DEMO UNIT, can anyone working at tmo PM me and run a check? Will this device stop working or possibly be blocked in the future? /sigh

Results from the Tmobile IMEI Status Check website says;

Congratulations! Your device is ready for use. Select one of the SIM cards on the previous page to get started.
The T-Mobile IMEI look up tool is for informational purposes only. The status of a device is subject to change at any time. T-Mobile is not responsible for any device blocking that is not disclosed or that occurs at a later date.

If you don’t have a T-Mobile SIM card for this device, you can log in to my.T-Mobile.com and purchase a SIM card and/or add a line. (Please note, it is possible the device may be reported as lost or stolen at a later time.)

I ran the IMEI on swappa, imeidata, checkesnfree, tmobile, ect and it comes up as clean, no financing.

imeidata allows for what appears to be a slightly more extensive check, including warranty check. These are the results from that check;

ESN:
Model: LGH811LB
MSN:
Suffix:
ESN Date(Prod. Date): May 13, 2015
ESN Go Date: May 18, 2015
Phone Age: 0 Year(s), 2 Month(s), 30 Day(s)
Location Code: N
Network Code: TMZ
Carrier: T-MOBILE_DEMOUNIT
CSN:
Blacklist (Lost/Stolen):

The blacklist check results;

IMEI:
IMEIData Database: Clean
AT&T (USA): IMEI is not recognized in AT&T
Verizon (USA): Clean (GSM or Activated by other User)
T-Mobile (USA): Clean
Sprint (USA):
Cricket (USA): Clean
Metro PCS (USA): Clean
Telus (Canada): Clean
Telenor (Sweden): Clean
Softbank (Japan): IMEI is not recognized in Softbank
AU KDDI (Japan): IMEI is not recognized in KDDI
Warranty & FW:

Suggestions, opinions? Return for refund and/or exchange might not be an option..