This is one of those vaunted system stability updates.
PS4 system updates have long since stopped adding meaningful headlining features. Mostly, they appear to just be making the system more “stable” and working behind the scenes to presumably fix bugs, glitches, and security loopholes and exploits before they take root.
The newest system update for the PS4, update 6.51, is similar. It’s one of those much vaunted “stability updates”, which means it does… well, nothing, really. Nothing front facing, at least. The official patch notes say that it “improves system performance”, and that’s it. Unlike the last update, which at least added iOS remote play, this one doesn’t really achieve anything.
The update is available now. As is always the case, if your PS4 is in Rest Mode, and you have automatic updates enabled, your system will have downloaded it, and you just need to apply it. Otherwise, you can go into system settings to force an update yourself.