Ah, I understand.
You can play both games than like on that Berzerk/Frency-modul from Jrok?
Btw, Andre, I sent you a PM some days ago 
No, you're completely mixing up stuff.
Imagine it is 1983. You are an operator and your Galaxian machine is not making the money like it used to do. Now you could buy a new cab, but that is pretty damn expensive. Then you look in a arcade operators magazine and you see an add for an upgrade kit that converts Galaxian to another game.
That is a cheap way to get a "new" machine and earn more on the same cab that you already have....
This is such a kit. These kit came in various "builds" ranging from simple EPROM swaps (remove old EPROMS, put in new one's) to extra PCB's like this (In this case put in a nice case).
You could not select games or even play the old game, it was a "one way" conversion, there was no need to play the old game, that was boring and done at that time
The Jrok boards are of course of very recent date and are complete replacements of an entire board-set.
All the original electronics of such a board-set (7 boards with Berzerk/Frenzy !) are "compressed" into a Jrok board.
You do not attach it to an existing board like the kits mentioned above.
