I was referring more to this.
https://www.tutor2u.net/economics/reference/measuring-national-income
But it seems people just use their own understanding of income/expenditure and then apply that at the macro level.
What does the income-expenditure identity have to do with the money? Surely, nothing at all, as it is a macro-level identity that holds all the time, even in barter economies, i.e. in the absence of money.
By the way, you might be interested to hear that the concept of income-expenditure identity, and from which national income accouting follows, goes back to Karl Marx.