Do you require a scientific study for any fact? If you bothered to do any googling, or whatever Mozilla equivalent of google is - this is in the top 3 results. https://9to5mac.com/2016/12/02/15-inch-macbook-pro-screen-re... Scaled resolution is defaulted on a huge amount of Macs.

I asked for data because humans are very prone to confusing things which affect them personally with the general case. Since Mozilla uses telemetry heavily I tend to trust their prioritization more than random self-selected commenters.