Isn't "developmentally delayed" lumping everybody who didn't hit the certain set of milestones into one huge, overbroad groups? For one, some of them may be "delayed" - i.e. they may catch up with these milestones later, but some, unfortunately, would never reach them, in which case "delayed" is plainly misleading. Is is a wrong definition or feel-good term that is incorrect in fact?
Nope.
Edit: I guess I should elaborate. Developmental delay is an indicator of a problem. It's not meant to be a final diagnosis - where possible, a reason for the delay is sought out. 'Developmental delay', like 'mentally retarded' is a symptom - it's just in olden days it was left there; the root cause was rarely sought.
Yes, the term can be misleading, and I don't like it for that reason. But it's not 'feel-good' nor incorrect in fact. It's an accurate description of what is happening.
I'd also strongly contest the 'nothing to do with better understanding', given that we now have multiple ways to classify mental issues, where previously they were all lumped into huge, overbroad groups.