The assumption is materially incorrect. The visionOS design component — which is the same as a design component that iOS has had for a fricken decade — does not exist in the contexts that 'a checkbox' covers in macOS, Windows or Linux.
This is a selection indicator. It is used in a very limited context to denote row selection in multiple selection contexts on lists and tables — and for nothing else. macOS, Windows and Linux would represent this state with a highlighted background (think selecting multiple rows with shift in the Finder). It is very notably not used for selection of non-mutually-exclusive options, a job that iOS usually ascribes to the very iconic, present-since-iPhone-Software-1.0 switch toggle:
In these contexts, the round checkmark selection indicator has proven to be remarkably unambiguous, especially because iOS (and visionOS as a consequence) does not have radio controls to confuse this with. While the representation of options that are mutually exclusive has varied over time, none of the representing visual elements used for it resemble macOS's, Window's or Linux's circular radio buttons in any of iOS's seventeen-year-span — you tap on a row in a set of rows, or you select from — in chronological order — a segmented control, an option among buttons in an action sheet, or recently from a desktop-like popup menu button, which is the default in SwiftUI for this kind of control.
This isn't a circle you need to think of and tap directly the way you mostly have to think about a desktop checkbox — it is a visual indicator for a much larger tap area in a very specific kind of interaction, one that, if one wants to talk trope familiarity, resembles its desktop counterpart in other ways (by highlighting the background of the selected row in a key color, for example).
tl;dr: is a design element that:
- Serves its purpose correctly;
- Does so in a narrow, carefully picked context;
- Has not largely confused people since it was introduced;
- Exists in a set of platform conventions where there is not a different element to confuse it with.
and if we have discourse whose entire basis is 'I have not looked at a mobile screen for seventeen years' we are just rage-baiting rather than having a measured discussion on UI design.
Edited to add:
- Yes, the labeling on the design toolbox is unfortunate.
- Yes, I'm aware the exception is that web pages have radio controls on iOS and its related OSes. Unfortunately, we encoded desktop metaphors in the spec before mobile happened as a thing that could have its own set of platform conventions. Either way, you may be happy to find that they do, in fact, use checkboxes that are square and radio controls that are circular.
- I have zero interest in entertaining meandering discourse on exactly the ways the OS represents mutually exclusive selection and their usefulness or usability or lack thereof. The point is that we should be professionals, and understand that contexts exist, and that this characterization of this platform element is ahistorical, and criticized from the point of view of a context it doesn't exist in — and for faults it never exhibited empirically. Everything else, I assure you, I have to think deeply about every day, and is not germane to the above.
- Likewise, zero interest in discussing if visionOS should follow desktop conventions rather than mobile conventions.
