These are F96T12/HOs

I knew that. The whole point of this picture is you can actually see the inside of the bulb.

Yep, GEs tend to have thin phosphor coating on the ends.

For cold temperature use...? What's the lowest temperature for their reliable start and efficient operation?

HO lamps are designed for use in the cold. They start in negative Fahrenheit temperatures, though not sure exactly how low. The "FOR COLD TEMPERATURE USE" is just put on there to circumvent the ban on certain HO fluorescent lamps. The ban does not apply to "specialty use" lamps such as lamps designed for cold weather use, so by adding "FOR COLD TEMPERATURE USE" on the etch, the otherwise banned lamp becomes perfectly acceptable. But of course since they're "specialty" tubes they're more expensive...

Thanks, Mike. That's an interesting explanation.
Regular PL fluorescent lamps (36 W) used in pairs in village streetlights here normally start at -20°C (-4°F). Thanks to climate warming, these temperatures are quite rare and very seldom go below that.
The situation might be different with your 120V power system though.