It's been awhile since anyone voiced an opinion here.

But - the Building Codes reference 1000's of Standards depending on the subject.

This subject under discussion here - 'lighting fixtures in T-Bar ceilings' is covered under Standard 25-2 [Metal Suspension Systems for Acoustical Tile & For Lay-In Panel Ceilings]

Section 25.213 [of Standard 25-2] - Lighting Fixtures
[There's lot of info here]

1. All lighting fixtures shall be positively attached to the suspended ceiling system.

2. Lighting systems weighing less than 56 pounds shall have, in addition to the requirements listed above, two No. 12 gage hangers connected from the fixture housing to the structure above. These wires may be slack.

So - there is no reason these 'additional' wires should have an impact on the T-bar grid.

And - this is where these building inspectors get their nebulous understanding of why additional wires are required on lay-in light fixtures.

Very few, if any, inspectors could provide you with a code section or document showing why these additional wires are required....it is just something they picked up over the years.

BTW - all these standards used to be published in the building code books...now-a-days the codes just reference the standards...which requires you to purchase these standards individually...quite pricey.