When people discuss the deflationary bias of bitcoin, I think they're implicitly comparing it to the current inflationary-biased dollar. That's not the right way to think about it.
You're talking theory.
But the comparison to the dollar is the real world, since we will continue to pay our mortgages and buy gas for our cars and food for our table with dollars for the foreseeable future. So the comparison with the dollar is a necessity.