While I would agree it's certainly not insignificant, fractional means, say, 1.5.x. A nice high-resolution display will be 2x, which will generally result in a nicer experience (largely due to how software deals with it or not). Now many people do indeed have displays where a fractional multiplier works better, but as a buying rec - try to avoid them.
If you put your scale to 2x you might as well save your money and buy an old 1200p screen instead of 4K. Biggest benefit of a 4k screen is more screen real estate, smoother text is of course nice too but imo secondary. When comparing image quality you also have to take panel type into consideration, a very good 2k IPS screen can still be cheaper and have better image quality than a entry level 4K with TN panel.
The nice 2x high-resolution display is generally significantly more expensive (just compare 4k and 5k displays at 27’’), so the advice isn’t wrong, it’s just not very practical.
I have one of these, a Samsung U28E590D which I'm very happy with in every way. That thing cost me 220 € (purchased in Germany), so I don't see what's particularly expensive about 4K 27" displays at this point unless you have some very particular requirements about shortest possible reaction time or precise color calibration.
The point is 5k 27’’ displays are significantly more expensive than 4k 27’’ ones (which are very affordable). And unless you prefer very large everything, running a 4k 27’’ display at 2x (meaning 1920x1080) is not desirable. But 5k 27’’ displays can be relatively comfortably run at 2x.
