You're confusing things. You could buy PSP games from the Vita store and the old browser store, but the PSP store itself was shut down in 2016.
The fact that the article still lists the PSP store as currently up and will be one of the things shutdown is entirely wrong, it's been shut down for years at this point.
Again unless they mean they're killing the old browser store(which was the only way to buy PSP games outside the vita), you can't feasibly remove the stores from both the vita and the PS3 and expect shit to function. The PSP was around since the PS2 it, predated a ton of shit including the entire current Playstation network.
The article and the shit surrounding has a bunch of technecal facts that are wrong, from one thing PSNow is very dependent on established PS3 networks including DLC. For example God of War Ascension requires an online pass, the PSNow version has that auto installed, but on the PS3 it's a separate DLC but either way requires access to the same server. if you were to remove the DLC from the store and make it defunct, you affect the PSNow version which streams the data from a Playstation 3 server. Same deal with trophies the lists are the same for PSNow and digital and physical PS3 games.
Taking the storefronts down entirely means removing almost all online functionality outside of P2P games. It means being unable to put shit on the cloud, being unable to download all your stuff. You get what happens with the OG Xbox Live where you just wind up losing everything.
The playstation account itself keeps records of what you have licenses too, it will even give you a message that you can't install certain things on certain consoles. but they all require the store to manage the downloads.