I'm comparing the behavior I'm experiencing with ReForm to this example from react-ux-form. In the react-ux-form example notice that first name is required but simply clicking into the field and then clicking out to cause a blur doesn't activate the error message. You have to actually "dirty" the field before the error message will appear.
An example use case where this is important is for a popup newsletter form. When the popup initially appears it auto-focuses the email field input. But a user who immediately clicks the popup-dismiss button is briefly shown an input validation error message even when they didn't mean to interact with the form at all.