The eternal problem with pedals/devices that have to make a "decision" about what to do with your signal based on the signal's present properties is that it takes time to make a decision, and sometimes even more time to make the most valid decision.
As such, gate-type devices have always had the challenge of make that decision fast enough so that the initial attack of a note is not lost, and so that noise doesn't leak in during the last few dying gasps of the note.
It's certainly not impossible to do it pretty transparently, but the challenge is still there. When the challenge is not met, that's when you get what Steve calls "coloration". I understand what he means, but will simply note inpassing that "coloration" is a term most often applied to contexts where there is a tonal change brought on by either adding harmonic content, or by "tone-sucking" and loss of some spectral content. Here, there is no real tonal change. Rather, there is a general amplitude change, which in some instances (e.g., loss of the initial attack where most of the harmonic content lives) can appear to result in a sort of tonal change. Small semantic point, but worth noting anyways.
The unit you describe (where the gating action occurs in two places. contingent on the signal properties at the start of the signal chain) is a smart piece of work. Certainly, the most reliable and easiest "decisions" to be made about the signal can be made immediately after the guitar. However, noise accrues across the signal path, from pedal to pedal. The smart thing, then, is to make the decision at the outset and apply that decision further downstream, at the same time as cleaning up the input signal enough to facilitate optimal processing throughout the signal path before the signal gets to that second gating point. It's a bit like raising your kids right when they're young so that the inevitable discipline problems are generally easier to manage with a lighter touch when they're in high school.
The intriguing thing, of course, is that the nature of the noise "problem" changes depending on where you are in the signal path. For instance, a big chunk of the nonmusical part of the signal at the input will be hum, whereas cumulative hiss starts to be a bigger deal downstream as gain gets added to the bits of hiss coming from pedals nearer the start. In essence, you need to adopt different strategies to eliminating the nonmusical parts depending on where the noise-reduction device is going to intervene.