This is a good idea. I use a catch-all domain for receiving mail. I never thought to set up DMARC & SPF until I received an email from a scammer attempting to impersonate the domain, but not any of the names I've used. I wonder also if it could impact the reputation/value of parked domains.
The article didn't mention Google's PostMaster tools:
This can give you a hint if your non-mail domain is being used elsewhere. I think it goes back 90-ish days, even before you had it set up.