More common names include testosterone suspension, testosterone base, TNE (testosterone, no-ester). It can be injected subQ. Certainly some of the steroid (ab)users do that. I'm not aware of evidence that you get significantly more aromatization this way than with IM. Absorption is a little slower.
It would not commonly be used for TRT because you need to inject at least daily, maybe even twice daily; the half life is pretty short, as I recall. The water-based injections can be painful because you're actually inserting small crystals that dissolve. You need larger needles too so they won't clog.
And no, I haven't tried it, but have some interest in it because of the possibility that you could better recreate a diurnal variation in T levels with suspension, perhaps taken in combination with an ester.