maxPercent is still useful if the desired max value is less than 300%. See https://searchfox.org/mozilla-central/rev/358cef5d1a87172f23b15e1a705d6f278db4cdad/toolkit/content/viewZoomOverlay.js#88-90 where we remove any steps in the zoomValues that are above maxPercent. I'll close this bug as "works for me" since we have found what was going on and it is just the two preference values that depend on each other.
Bug 1658482 Comment 3 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
maxPercent is still useful if the desired max value is less than 300%. See https://searchfox.org/mozilla-central/rev/358cef5d1a87172f23b15e1a705d6f278db4cdad/toolkit/content/viewZoomOverlay.js#88-90 where we remove any steps in the zoomValues that are above maxPercent. I'll close this bug as "invalid" since we have found what was going on and it is just the two preference values that depend on each other.