That was a feature designed to fit more options on smaller screens. I personally like it and find it helpful.

It messes up any attempt to recollect of the locations of certain features in the bar. Some iterations of the ribbon even fold groups into menus under single buttons, so the exact path to feature then depends on the width of the window. This turns the ribbon into a pretty inconsistent user experience.

I don't recollect the location of features by their spacial location, I recollect them by their place in a hierarchical ordering. The exact path to a function is always preserved, as the keyboard shortcut for that item is defined by that path.

Ribbons (in Office, at least) change that very hierarchy depending on window width. For example, take the Home bar in Word: the "Editing" and "Style" groups collapse to buttons with submenus before the width of the window is reduced to half screen width on my computer. This affects keyboard navigation in the ribbon bar, too, of course.

This doesn’t actually change the hierarchy of commands, as evidenced by the fact the keyboard shortcuts stay constant. I appreciate hiding these first before Font, since I use Font more than Styles or Editing.

What hierarchy is supposedly staying constant? Keyboard shortcuts have no hierarchy.

Keyboard shortcuts for functions in the ribbon map directly to their placement in the ribbon hierarchy. Tab, section, subsection, etc. You press alt and then a series of one or more letters that define the path to that item.