Same thing happened to me. I was a little disappointed when I opened the package because I like using the .625 barrels on retro builds, and DD is (or at was) the only people who made CHF 1:7" lightweights.
I think the listing on the website is correct. DD has discontinued the .625 OD at gas port barrels, and Brownells is flushing out the old stock. A few months ago there was a similar sale on Brownells for the 16" carbine LW, .625 at gas port. When I ordered then I got what I ordered.
What I'm sure happened is they oversold the old lightweights and shipped the M4 profiles in place. Brownells does not have live stock tracking, so they do oversell. I remember during the Newtown panic I placed an order for a VLTOR upper reported in stock, and then just never heard anything again, no charge, no ship, no comms.
It would've been courteous of them to call and give a heads up regarding the item switch and offer a chance to cancel the order, but I'm not complaining about getting a DD CHF barrel for $150. Despite the carbine gas M4 profile being the least popular profile, it's still a good deal for a good barrel.