Interesting if so.
For others just joining us the SDK = software development kit, aka what Sony gives/sells to devs to allow them to make code for their devices.
Back in the 8 and 16 bit era they often contained very detailed hardware listings (a few are available for the megadrive if you want to get them)
http://www.romhacking.net/documents/277/
some others
http://www.romhacking.net/?page=documents&author=1413 and others are available elsewhere on the internet.
As time went on this hardware detailing became less and less as it was more about software based approaches than knowing the hardware (far easier to code in general, far easier to port things between PC and console and other consoles and...). This process was more or less complete by the PS2 (and as this is now the PS5, which in many ways is a glorified PC...)
At one point the hardware documentation and codes provided would allow people to possibly figure out exploits (assuming the keys were not outright there -- today devs, testers and suitably blessed reviewers get specialist kit with its own keys that are not the same as the general public ones).
Today they are mostly useful to get an insight into the formats that Sony provide for devs to use -- if you ever go in the ROM hacking sections around here and see people discussing common formats that different games from different devs use then chances are it is something provided by the console maker for devs to use to not have to reinvent the wheel). Sometimes such things even come with plugins and code to turn common normal formats into the game specific ones (the DS for instance saw part of its 3d kit leaked long ago, and thus if you can find what was then already an old version of a commercial 3d modelling program you could install the plugin and generate a 3d model in the format the console used), usually graphics, video and audio are what gets looked at here.
With a hacked console you can also potentially use them to make your own homebrew, or if any game code is leaked then if it is of a similar timeframe you can probably compile that too (older stuff and newer stuff might do things suitably differently that it is hard). Any homebrew compiled using these also tends to be hard to distribute -- we saw with the original xbox that most used the Microsoft SDKs that we have one of the more complete collections anywhere for, and that is why you don't have simple downloads of homebrew/PD games like we have for... every other console really and instead get to use strange FTP setups, logins to private servers, torrents and other such things otherwise normally associated with the ROM downloading set.
I would note for both of those uses that this is likely a pre release kit as well, and while it could be a continuation from the otherwise stable PS4 dev setups then traditionally pre release tends to have minimal helper formats and be somewhat clunky compared to later stuff (early stage code and all that).
They tend to be of minimal use for people looking to find exploits in the console, especially as most things they cover will only mean you have game level access to the hardware which tends to be more restricted. So not useless but of minimal use.
Looking at such things might also disqualify you from participating in certain projects -- see the now rather famous quote from the dolphin (gamecube and wii emulator) devs when various Nintendo SDKs leaked and they noted that anybody caught admitting to such things would be booted or prevented from joining. See also "clean room reverse engineering".