Does she not know that he actually genuinely doesn't care about any of the particulars? Does she not know his food preferences, if he has any?

This seems like serious a bidirectional empathy problem, if it was an empathy problem, and more hers than his, if the account is accurate.

It sounds to me more like a communications problem. "The hard part about dinner for me is deciding what to make," she says. "Can you please take on the burden of deciding."

If it's not something like that, Matt is being too kind on his ex, or leaving something out of the story, because "I am going to have you arbitrarily do pointless stuff or it's going to wreck our marriage" is not what marriages are built out of, and neither is, "When you both say you don't care much about something and show you don't care about something, I am too emotionally and rationally clueless to believe you." That's on her.

However, if she was asking him to help her make a concrete plan, and she couldn't articulate that aspect clearly and he also didn't have the empathy to pick up on it--well, that's shared responsibility, and maybe a bit more on him than her, because knowing what your partner finds tricky is a core empathic competency.