That doesn't gel with my experience, 1080p was the de-facto resolution for 24" monitors but 27" monitors were nearly always 1440p, and switching from 27" 1440p

That doesn't gel with my experience, 1080p was the de-facto resolution for 24" monitors but 27" monitors were nearly always 1440p, and switching from 27" 1440p to 27" 4K requires a fractional 150% scale to maintain the same effective area. To maintain a clean 200% scale you need a 27" 5K panel instead, which do exist but are vastly more expensive than 4K ones and perform worse in aspects other than pixel density, so they're not very popular.