My take is this:

PP's are to raise $X amount of dollars to fund assorted activities - BFS, drilling, etc.

Regardless of the share price (and therefore how many shares Ernesto gets for any given PP tranche) as an investor it still costs him the same amount in dollar terms. Those PP dollars are actually paying for stuff like the BFS etc.... not the shares Ernesto nets in exchange.

So if he commits less PP dollars, it's because less needs to be spent on real life activity.