I think there's an interesting distinction to be made between wealth that naturally produces more wealth (like owning a successful business, or a share of it) and wealth that doesn't (like owning a fancy house).
And (something something Piketty r>g something) there is something to be said for measuring how "productive" wealth is distributed, as distinct from things like gold and housing and bank accounts.
But:
That isn't what Ruccio is proposing, nor is yours or anything like it the reason he gives.
My pension funds are approximately 100% equities. They will, if the businesses they're invested in do well, grow. They provide me, in principle, with a tiny amount of power over those businesses (though I'm not sure I have any way to exercise it). But Ruccio wants those excluded from my net wealth when calculating his statistics.
The money in my bank account is (as far as I'm concerned) just cash. I suppose my bank gets to use (most of) it for productive investments, but it makes no surplus for me. But Ruccio wants that included in my net wealth when calculating his statistics.