Yes, that's the idea. Force specialization in the attack sphere, reduce the attacker population with prerequisite knowledge as an entry barrier, simultaneously shrinking the targetable hosts.

Yes, I get that electronic signaling is electronic signaling, and none of it is actually different, at the transmission layer. It's just more DSP and more fast fourier transforms under the hood.

Yes, technical barriers can be eroded with adapters and facades, but it's an added cost to attack, and reduces detective work in that you have to know someone to jump the learning curve and enter the attack envelope. That means detective work can happen within a smaller social graph, and that alone becomes a deterent from sharing information, because everything becomes need-to-know, and insider awareness is a give away for inside jobs.

It's also easier to stamp out, and ostracize insiders, if they have loose lips or have a tendency to lend and give away the car keys.

Not everything needs to be as cheesy as Encryption DRM for optical movie disks and video games. For critical infrastructure safety is important enough to warrant independent military-grade safe guards.

Do military protocols fail? Yes, we have the enigma machines sitting in enough museums to prove it.

This in not an XKCD "too many standards can be solved with one more standard" concept. Isolation and specialization can be effective defense concepts.