This is a fascinating topic and gets my mind going with a few thought experiments to tease out what could reasonably be considered a grid. So here is a test:
Would you consider a modular synthesizer to qualify as a grid interface?
A Monome Grid is a generic interface that takes a single primary user interface element and uses repetition to establish a grid/matrix. But I have seen some fascinating and beautifully creative extensions of all the ways that single interface element can be employed to serve very different functions. But a core aspect of the grid seems to be that the individual and repeatable elements work in concert with each other.
In a modular synthesizer, it seems you could make the case that there are similarly a few core elements that utilize repetition in a similar manner. At the macro level are modules themselves. At an intermediate level are maybe the CV jacks and the common controls. At a micro level is a linear or non-linear CV signal network. A modular obviously meets the tactile feedback criteria. The knob positions, displays, sliders, screens and LEDs would seem to meet the criteria for visual feedback. Not sure exactly what you mean by “decoupled” but the reconfigurable patch-ability might meet this criteria.
I think there is even a uniformity in the knob/jack layouts in some of the first mature modular systems (i.e., decades before the eurorack era) that really look like grid interfaces.
