I would assume his net value is mostly invested in public and private companies.

Presumably it would affect the amount he is actually able to immediately use to support those in need.

He's the richest man in the world. He has enough liquid assets to aggressively pursue charitable giving if he wants to.

I doubt many people would question that he has significant liquid assets, I was just pointing out the relevance of the question. For a business owner on his scale, I'd imagine that the vast majority of his wealth would be tied up in business ventures.