This is problematic even for people who don't mind linking to an online Microsoft account (I'm one of them). There is a long-standing Windows bug where local user directory names are created using a truncated version of the online account's name. This is rarely what you want. The work-around has long been to create an offline account first to name your own local directory, then convert it to an online account.

This will break that work-around, and this is universally bad.