IF your MV is registered as a TxFMV (Texas Former Military Vehicle) then most probably certain aspects of the OPERATOR'S VEHICLE INSPECTION KNOWLEDGE will be perceived by the Testing Official (may not be a SHE) as NON-COMPLIANT with current production vehicle standard since most MV's pre-date the current design standards.... Even though as a TxFMV your MV would NOT be "required" to comply with those current standards.
IF you choose to register your MV as a TxFMV with the "NO TAG" option, that will be viewed as your FIRST "perceived" violation.
IF you choose to register your MV as a TxFMV you are NOT required to display the annual windshield decal (only carry in in the vehicle to be presented on demand) THAT will most likely be your SECOND "perceived" violation. And your THIRD "perceived" violation would be presumption that with no windshield sticker than you most probably have not had the vehicle inspected either, when completely LEGALLY you would NOT be required to have a TxFMV inspected at all!!! REMEMBER, the Testing Official is more than likely an reasonable "EXPERT" in commercial vehicles.... and NOT so much knowledgeable in the various EXCEPTIONS to an assortment of Texas LAWS that TxFMV's enjoy.
PLEASE refer to the TxFMV LAWS Thread linked in my Signature Block below.
In summary......
It's their game, their rules... whether you're right or they THINK you're wrong.... Is the fight worth it???
https://www.youtube.com/watch?v=rN0T5tyJlo8
Carry on.