Painting - Flat to cover Semi-gloss question

This is new drywall, was primed with 2 coats of PVA/Drywall primer, then 2 coats of white latex semi-gloss....decided I don't like the glare of the semi-gloss, plus it shows every little imperfection in the drywall. Paint has been up one week....no age, dirt, grease, etc to worry about.

So, I'd like to go back over it with a white latex flat paint.

Am using a Grayco airless sprayer.


Question I have is:

Should I re-prime and then do the flat, or can I just do a couple coats of flat right over the semi-gloss ?

Talked with 2 different paint stores:

One said "Gotta prime...use Kiltz, then paint"

Other said "No problem, it will bond just fine, go ahead"

Is the first place right, or are they just pushing primer ?

Thanks guys......a painter I ain't........

If the surface is that new, just shoot the flat on top of it.

Thanks....