Earlier quoted context omitted.
I think it’s a good practice to keep the abbreviations the same when talking about in the same context. It makes clear the ratio being talked about.
I'm definitely not in the world of finance, but in day to day conversation, I have to stop to think what one hundred sixty thousand million means. If I hear one hundred sixty billion, then I immediately understand. Even if I had previously heard five million then heard one hundred sixty billion, it is obvious that billion is 1000x a million which clearly makes it a bigger number. This is what I meant by unnatural.
In writing you can't do that as easily or effectively, so I think keeping the abbreviated units the same is effective writing.
In fact stating income in thousand millions is exactly how financial statements are formatted. In alphabet's 10k (at https://www.sec.gov/Archives/edgar/data/1652044/000165204419...) there is a table showing that the google segment had $136,224M in revenue, while "all other bets" had a total revenue of $595M. I suspect that the SEC would have some stern words for alphabet if they expressed on measure in billions and one in millions...