Magnus, Let me explain...
If Peter requires the information to be displayed on a page. The functionally he must need is for it to be displayed on the page and then make use of this information. For instance, he cuts and pastes the id and uses it on gedmatch. This is why he needs it displayed.
But if he doesn't use it this way, he only needs to "have Google find a keyword" on the page, this can be done without having it displayed.
The decision to decide if something is displayed or not displayed is made completely independent of the decision to use keywords in the HTML.
Because these are two completely independent decisions, I would like to concentrate on the one that involves it being displayed. What process requires it to be displayed?
I have no problem with the general principle of having more keyword data the better if this makes any difference. I don't agree that it all needs to be displayed.