In fact the resolution of GFS is 0.25°.
1° being 111km, 0.25° is ~ 27 km. But this is when you consider the resolution in latitude.
As far as I know when the NOAA presented this model they announced its resolution in longitude at Washington latitude.
This sketch explains how you find 22 km.

So now most model resolutions are displayed in longitude.
The model IFS of the ECMWF which is the one shown in Windy has a 0.1° resolution. With the same calculation in longitude it gives 9km.

Note most of the weather apps using this model of the ECMWF show in fact a free version called “WMO essentials” with a downgraded resolution of 0.5° or 43km. The fees for the 0.1° version that you get in Windy is very expensive.

Another question - if the model resolution is predetermined by itself why some apps use GFS 27 and yours use GFS 22? Where the difference come from?

Thanks.

The resolution of weather model cannot be changed by Windy of course. In the free or the Premium version, the model resolution is basically the same.
It was said that the images of weather prediction maps would be improved, providing a better granularity.
This is more obvious with the higher resolution models (HRRR, AROME, ICON D2) in mountains.

Temperature w/customized color scale

Even with the models that you mention, try to make a screenshots when you are logged in and out to see the difference.