Scouts never stopped being a thing.
The section on the different types of Primaris supports the previous statement from GW that chapters are still making standard marines.
There is also a bit about geneseed where it is said geneseed is a finite resource that can no longer be produced. I know it’s rare and very important, but I thought it could still be made, indeed I thought cawl had made new geneseed for the Primaris marines? I guess not.
It confirmed that veteran Primaris can join the 1st company. It’s mostly shown as Intercessors, although the from the ultramarines supplement it is stated their 1st company has veteran Intercessors and Inceptors.
I interpreted that as being that they can't make any new geneseed from scratch. Each new piece must have been developed from an existing Progenoid gland, which may have been tinkered with, or regrown normally.