That's highly unlikely, the 27" 5K defaults to "looks like 2560x1440" while the 27" 4K "looks like 1920x1080", in other words much less content on the screen.
macOS only properly supports 100% or @1x scaling intended for use with ~110ppi monitors, and 200% or @2x for "retina" displays with ~220ppi.
If you have an intermediate ppi like a 27" 4K then @1x everything will be really small, or @2x you'll not be getting much screen real estate, or you must use one of the indirectly rendered scaled resolutions with the well-known disadvantages of not pixel-perfect rendering and additional system load.
Some people ignore these issues and use scaling, other people like me don't like these disadvantages and will only buy monitors where the resolution fits.