I'm not saying he CANNOT use the spacing he suggests, but...I have a client that is doing an ICF home with a 6" core that he is claiming that he does 24" o.c. spacing all the time.
I worked on several forensic jobs over the years here in Houston involving tilt-up buildings, where the reinforcement was below - sometimes WAY below - the minimum required by ACI 318, even back in the day. At the time they were doing this construction, the late-70s/early-80s, light commercial tilt-up construction was newfangled, and as in many cases (like ICF, I suspect), the purveyors claimed they "discovered they can get by with such-and-such." This is necessary for them in order to remain competitive with established systems - it's really their only selling point, after all.
Well okay, so they would put in the 4" rebar at, I dunno, 16-inch centers or whatever, and over time with an eccentric roof ledger load, e.g., the panels would bow out like crazy.
I don't personally think that anyone ought to be exempt from rules of standard practice, using the rationale that "this is a pioneering, new system" and "we do it this way all the time." I've seen such systems come and go (some of them have stayed, of course), and eventually everyone learns that you can't really cheat the rules of the natural world. You can always do something WRONG "all the time," and it's only much later that someone has to pay to have it fixed, after you've retired to Costa Rica.
Like I said, that's just MY opinion. If I were reviewing plans on that basis, that's what my comment would be, and that would be my rationale. And it'd almost surely get shot down because "everyone knows" the contractor knows more about all this stuff than anyone else on the planet.