To the OP;
The cam button suggested by your builder was most likely in the form of an inexpensive safety device. In “your” application the block face carries the thrust load. The button is simply used to control travel in the case of driven load changes that create cam walk.

In the case of a broken chain at high RPM, the driven load change between the crank and cam is so rapid that it will literally try to pitch the cam OUT of the block. Even a plastic button in your case is sufficient; you can buy them for less than 15.00 SHIPPED!

Your engine builder is looking out for your best interest…….OR………you could listen to keyboard builders and simply use the option to forgo the button. But food for thought – if your technical adviser uses an aluminum button and suffers “avoid the aluminum one's like the plague - they will gall up and little bits will fall off into the motor” – syndrome, then your may want to use a different resource - I don’t know, just a guess…