I don't know the timelines between the SFI H&N requirements and the existence of the Isaac device (I'm sure I'll hear it), but I find it tough to believe that the single-point-of-release requirement exists with the very intent of excluding the Isaac.[/b]
According to the "archive news" on the SFI foundation website, 38.1 was announced in Jan 05. The search function on this site has Gregg promoting the ISAAC in Nov 02.

Seems extremely clear to me that the SFI 38.1 wording was created to exclude the only device that posed a real threat to HANS at the time. Others have since designed devices that do meet the physical requirements of the spec.