For me, I often get bothered by the philosophy of “you can’t just because you can’t” because it discourages me and other members from doing experiments.

that's how i feel as well! some may frown on it, but by experimenting with various ballast/bulb combinations i've discovered many that work extremely well even if not specified for the way i'm using them, and as a result i've gotten a number of fixtures working again, when they had been considered "dead, and we can't get ballasts for it anymore". when it comes to the F60T12 tubes, i have multiple cases of them i'd like to put to use, and also plenty of magnetic instant-start ballasts. if the 2 can coexist happily, i'm fine with the reduced light output from running them as "non-ho" tubes. i recently did find a stash of actual ho ballasts, the big heavy ones rated in number of feet rather than type of bulb... so at least some of these F60T12s will be operating as intended. that's no reason to dismiss using them with the ballasts i have more of, though! i would note, these instant-start ballasts do say they're compatible with F60 tubes, they're just intended for single-pin slimline ones. considering that they're happy to start and run the ho tubes, i'll see how long they hold up, i suspect they'll last just as well as they would with actual slimline bulbs.