You advise to be human and kind but automatically categorize "difficult people" as being on the spectrum? And no worry, some engineers don't need to be on the spectrum to be difficult. Conversely, people on the spectrum are not inherently difficult either.

But I do agree: communication is key. Craftpeople can have trouble taking the team or the business priorities into account. Being the manager, you have to take the other parties' side and talk about the non-technical problems: time to implement (= money and unavailability of the engineer), additional complexity, fragility, making changes more difficult... Convincing is always better but if you argued to no avail, you have to impose your decision – being careful not to be the asshat in the mix.