@Brecht Van Lommel (brecht) let me give you a better explanation of the changes to the checkbox-distance-to-text change:

Before, the text in Blender was very far away from the checkbox compared to other apps I could find:

The fact that the text was as far or further away from the checkbox as the next checkbox, meant that the visual grouping wasn't optimal:

Compare it to this - the text is much closer to the checkbox it belongs to, compared to the distance to the next one, making it easier to see that the text belongs to one specific checkbox:

The other reason, is that when using headings, it works much better with this change. Let's look at a before/after:

This version looks like a checkbox in the middle, with some text flying around on either side:

Compare to this. The text clearly belongs to each checkbox and the heading is nicely different, separated:

This information should have been added to the design task or the patch description above. But, perhaps this gives you a better idea of the rationale behind this particular change.

I don't know. Most of the apps I've checked here do have checkboxes maybe a bit closer, but not anywhere near as crammed together as Mac OS, such as:
VSCode:

@William Reynish (billreynish) I think it's just an issue with smaller UI scales, which doesn't show when it's 2.0 as on macOS retina displays.

Fix for excessive rounding:

diff --git a/source/blender/editors/interface/interface_widgets.c b/source/blender/editors/interface/interface_widgets.c
index 0aed84f..38c9a24 100644
--- a/source/blender/editors/interface/interface_widgets.c
+++ b/source/blender/editors/interface/interface_widgets.c
@@ -4146,7 +4146,7 @@ static void widget_optionbut(uiWidgetColors *wcol,
   uiWidgetBase wtb;
   rcti recttemp = *rect;
   float rad;
-  int delta;
+  float delta;
 
   widget_init(&wtb);
 
@@ -4159,7 +4159,7 @@ static void widget_optionbut(uiWidgetColors *wcol,
   }
 
   /* smaller */
-  delta = 1 + BLI_rcti_size_y(&recttemp) / 8;
+  delta = 1 + BLI_rcti_size_y(&recttemp) / 8.0f;
   BLI_rcti_resize(
       &recttemp, BLI_rcti_size_x(&recttemp) - delta * 2, BLI_rcti_size_y(&recttemp) - delta * 2);
   /* Keep one edge in place. */

Before and after with UI scale 1.44:

@Brecht Van Lommel (brecht) I see, your change seems to make sense.

@Brecht Van Lommel (brecht) I tried this change before, but issue is that it scales down checkboxes by 2px I think. That in itself I wouldn't mind, but it breaks vertical alignment with panel headers, e.g. at 1.0 DPI:

@Brecht Van Lommel (brecht) turns out the issue was that DPI and zoom got basically applied twice in the padding calculations, so I guess rounding errors added up. Once by using the rectangle height for the text rectangle changes in widget_optionbut(), once by the regular widget_draw_text_icon() text padding. Now widget_optionbut() has full control over the padding.