Wasn't the actual PSP store closed down in like 2016 or something?
I'm a little confused by what they mean too.
I believe their PC software Media Go, while updates were discontinued, still functions. It's somewhat unknown but I would've adored to have had this same function for Vita. You can download your games and media from PSN directly to your PC, keep them there as a backup, and then transfer to your PSP later. When the PSP store on the system was closed I remember this being mentioned as "this will still work", so I wonder if they're finally going to kill it off.
I suppose the second possibility is the removal of PSP content from the PS3/Vita stores?