>>Insensitive as in "not as critical" or insensitive as in irrelevant?<<
Meaning not critical, verging on not relevant. Large differences can have some effect but the design doesn't intend requirement for futzing with floor gap height. The Griewe scheme is now primarily internal via the cartridge and the finger vents on the bottom. You can find *some point* in the gap range where approaching no floor gap is not good but short of heading hard for zero, it should not be a critical factor. You need 1/4" gap or more. You'll notice in Zu's own photographs of the speakers, the spikes are quite tall.
>>Also I feel like presentation has been different higher vs. lower, though in fairness I didn't have it perfectly balanced when they were higher. I broke out the bubble level when I was working for the jewel case height.<<
Depending on many other acoustic factors you might be sensitive to differences in presentation associated with small changes in driver height. Or, as I said, if you head for zero on the floor gap less than 1/4", things will change. You may notice diffrences without having a clear idea which is actually better from a fidelity standpoint. No one can tell you what you're hearing isn't heard, but from a physics standpoint, Soul's design removes the floor gap from performance influence from 1/4" and taller.
Phil