Not over the last few months, obviously. But in general I've never known a serious trader who didn't maintain a cash balance at some non-trivial level, if only to maintain liquidity for low-latency bets.
But regardless, the point was that all the "cash" you see in your investment accounts (even if you, personally, don't carry any) is predominantly treasuries and other short term high-confidence debt. Everyone owns treasuries, it's only true that very few people "buy" treasury notes.
Well, your statement was that a "meaningful population of the target audience" did not "have any meaningful amount of treasuries in their portfolio". And that's wrong. Basically everyone holds treasuries. Some people don't. Most people do.
You're goalpost-moving to the converse of your point, though. You weren't claiming that there was merely a meaningful population who wouldn't benefit, you were stating that there was NO meaningful population that would. Go check. And again, that's wrong.
But regardless, the point was that all the "cash" you see in your investment accounts (even if you, personally, don't carry any) is predominantly treasuries and other short term high-confidence debt. Everyone owns treasuries, it's only true that very few people "buy" treasury notes.