Your point 1 is exactly the question I came here to see answered. The article actually claims "Another benefit to unified text fields is getting the user’s info

Your point 1 is exactly the question I came here to see answered. The article actually claims "Another benefit to unified text fields is getting the user’s information in a format that you want without sacrificing ease of use or speed" - but I want to be able to use the forename only (so, for instance, I can address newsletters with Dear Jacob). It's certainly not about validity / invalidity of names. And yes, that's not a perfect situation - some people may prefer Dear Mr Aldridge or Dear Jake (ugh). But as long as I recognise that shortcoming, and (which I do) only require a single name (so people with only one name are not ruled invalid), I don't see how a unified field gives me the format I want.