The continuous diaphragm adjustment gives fractional stops of exposure control -- you can do the same by not using f-stop timing for your test strips (if you expose 3, 6, 9, 12, 15, 18 seconds, you're going up by 1, appr. 1/2, appr. 1/3, just over 1/4 and just under 1/4 stop, vs. 3, 4, 6, 8, 11, 15 giving nice appr. 1/2 stop increments). Most darkroom workers who learned when I did were already incrementing test strips in fixed time, rather than f-stop intervals (I first heard of f-stop timing in the oughties, and wondered why I'd never run across it before, though it was probably around in the 1970s when I was learning this stuff the first time). Fixed intervals is easier (set darkroom timer, run timer for each interval as you move the mask), but f-stop in half stop increments is more likely to save you a test, maybe two.
My own preference would be for (at least optional) click stops on the diaphragm -- that way I don't need to crane my neck and/or bump my head (potentially requiring refocus) to get close enough to read the scale in safelight conditions. Almost all click-stop diaphragms can still be intentionally set between clicks, if needed, but it's much easier to stop down from focusing/cropping to exposure setting if you can just "f/4, four clicks, f/16", light off, set the paper, start the timer.
