This patch allows the use of floats when specifying text sizes.
This might seem like a solution in search of a problem if you only consider running Blender in English using the supplied font.
But best to first consider that "Resolution Scale" basically changes the size of the grids that UI elements are laid out into. So doubling the scale will give us larger icons and larger boxes that contain text. But how big the text is inside those boxes, relatively, is set in Themes / Text Style.
The most important reason to change things in Themes / Text Style is to accommodate a change in font that has different metrics. If you were to change the Blender font to one that has wider characters you might want to decrease the point values. Similarly if you use a font that has tall and thin glyphs (like with many Arabic fonts), then you'd want to increase the point sizes there.
And having greater granularity can come in handy. For example if you were to swap out the supplied font for one from Google's "Noto" family you will see that all the text looks slightly smaller, just because of the difference in how the characters are designed. So you'd want to increase the text size a bit. But changes of a full point size are too much.
Note that although FreeType supports sizes and positioning with fractional values with a resolution of 1/64 of a point, it does round the requested fractional font size so that the resulting EM square has whole pixel values. So the effective resolution is less than 1/64 of a point. But this patch does generally effect a visual change of an average word with changes of 0.1 of a point, even at 1.0 interface scale.
Note that this should not require any versioning code as Blender converts ints/floats when needed during file load.