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.
Verbal conversation gains the context of audible emphasis on the difference. Rhetorically, you are able to say "Waymo has revenue of 5 million dollars, while Google has 160 BILLION dollars." (imagine the all caps being dramatically stated, possibly a la Dr Evil in Austin Powers).
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...
