It looks like that advice is specific to iOS. Recommendations elsewhere specify that both device-width and initial-scale should be included for compatibility with all mobile devices, e.g. https://developer.chrome.com/docs/lighthouse/pwa/viewport/
That is similar to what I was trying to convey. Breakpoints are just that though, the _point_ at which style rules _break_ into different groupings. Viewport _ranges_ exist between breakpoints.
It is also a pet peeve of mine that breakpoints get referred to as "mobile", or "tablet". Very much agree on making content work at all screen sizes, and picking points where it makes sense to "break" at different viewport sizes depending on the content. At the end of the day, it is very arbitrary.
The CSS Media Queries Level 4 spec actually includes fractional pixel values as part of the examples for browsers which do not yet support the range syntax: https://www.w3.org/TR/mediaqueries-4/#mq-min-max
> One approach to work around this problem is to increase the precision of the values used for the comparison. Using the example above, changing the second comparison value to 320.01px significantly reduces the change that a viewport width on a device would fall between the cracks.
The way I tend to work with media queries is not writing them directly but rather use a mixin (when using SCSS) or a media function (CSS-in-JS). That way, this weird quirk can be documented just once in an application, leaving anyone curious enough with the explanation. There tends to be an 'upTo(breakpoint)' function which is an exclusive range, and a 'from(breakpoint)' which is inclusive.