You've missed this @CircleSeven, but I've talked a bit in the Discord about what Gray is doing.
Gray buys LPTVs for two reasons:
To provide UHF transmission in the core metro area for a VHF station that cannot move to the UHF band at full-power (what I call a "U-relay").
To provide additional translators, even for stations and regions where traditionally this has never been a consideration, at the outer edges of station coverage areas.
I don't know how many LPTVs Gray is buying for ATSC 3.0, a la their Tallahassee test bed. However, I do believe the strategy also has to do with looking down the road and the idea of a more cellular signal topology (multiple transmitters ensuring a high SNR within the defined coverage circle of the primary station). Along the way, they get UHF sticks that can serve a high percentage (if not all) of the viewers of the DMA and their flat-panel indoor antennas and, where necessary, can serve as ATSC 3.0 transmitters if so desired.
In Nashville, for instance, Gray has contracted to buy three different LPTVs: 15 Nashville, 29 Lebanon–Nashville, 29 Lewisburg. Lewisburg is a translator; it's toward the southern edge of the WSMV contour. 15 Nashville could easily be a U-relay. (RabbitEars lists the first two as U-relays already!)
This is actually some cutting-edge stuff and shows that Gray sees value in improving signal coverage. It may be one of the largest efforts to commission new TV translators in 20 or so years at least, and a lot longer than that when considering the location in the eastern US of many of the stations that benefit.