To me, SolarEdge's "Rapid Shutdown kit" seems to be a solution to a non-problem. In otherwords, money you spend to solve a problem the NEC doesn't require you to solve.
The rapid shutdown requirement doesn't require you to de-energize circuits within a piece of manufactured equipment. It's main intent is to require you to de-energize field-installed circuits.
And even without this rapid shutdown kit, if you open the DC disconnect, you already disconnect the field-installed circuits from the capacitors in the inverter. The optimizers then default to 1 volt per unit, and the circuit is brought down to safe levels of DC voltage meeting the NEC.
In the event that you have numerous inverters, the only way to initiate rapid shutdown within the time limit is to turn the DC disconnect off on each one of them. Given much more then ten inverters, this obviously cannot happen within ten seconds. What really would be useful, is to have a single action initiation of rapid shutdown. A master AC disconnect almost does this, except that it doesn't guarantee meeting the ten second time limit.