For reference, I have it wired in series with the 303 and 304 wires which go to the MX3660 input which AFAIK is low voltage and separated from the rest of high voltage E-stop stuff (unless I’ve missed something).
The E-stop button still works as it used to and pushing the ETS all the way down also initiates an E-stop.
I would imagine that some of the other series of machines have a similar input somewhere so that no one has an unnecessary crash. I see no reason to ignore these two wires on your install of a similar ETS.
Yes, we should be protected by it being NC but if the first switch/contact shorts out to closed and never opens upon contact, then at least you have a second one to stop before you break carbide or crash…