26" McGowen barreled 6mm Grendel upper

[Tex Nomex]

I don't understand how those Superlative gas blocks are any different than a leaky traditional gas block, which I have personally seen (more than once) turn a rifle group into a shotgun pattern. The high pressure gas that's exhausted from them could have been used to propel the bullet faster, or at least present a similar volume of gas at a similar pressure to each bullet in a group.

The SA gas block can be used either way, as a traditional gas restriction/cut-off or as a pressure release to atmosphere.
The SA piston system is the same.

Here's Michael Bell's SA Gas Block Test Video It's small sample sizes, but it seems venting allows for more consistent bullet velocities overall and average velocities are the same as a non-suppressed rifle with the adjustable block dialed wide open/non-vented. BCG also runs cooler when vented.
YMMV