So why isn't there a plague of it in Kenya? I don't know, but a lot of these things have some element of truth but have been distorted by continual repetition out of context to the point where I just don't know how important it is.
Although it isn't obvious what makes a running shoe and what makes a walking shoe.
If you've ever tried running anywhere past a few meters in a walking shoe, you'll know the difference!
A bit stiffer in the sole (makes a useful difference on some terrain by distributing pressure from small bumps) and usually a slightly chunkier upper with more and higher suede/leather/whatever that's not mesh which will keep out damp (particularly the likes of longish wet grass) where a mesh won't. So not as flexible and not as breathable, but with useful payoffs.
The old Scarpa Helium is IMHO clearly a walking shoe. Helping out at an O in winter a few years back I'd worn my Heliums as I wasn't doing a course (not very ethical if you've put the controls in place setting it up!) and we ended up in a hurry to get all the controls in before it got dark, and being in a hurry I was running, and it really told after a while, sole stiffness being the really salient point.
Having said all that, there's nothing problematical about walking in a running shoe as long as hard, uneven ground doesn't result in sore feet (first time I did the Aonach Eagach was in a pair of running shoes and my soles were a bit fried at the end of it, TBH) and as long as you don't mind almost any contact with moisture getting through (lined runners excepted there). Plenty of occasions I'll prefer to walk in runners (or sandals) rather than walking shoes, but running in walking shoes really doesn't work over any appreciable distance (i.e., more than a couple of hundred meters).
In summary, walking shoes are somewhere in chunkiness between a trainer and a boot, part of that being the lack of an ankle cuff but often in sole stiffness and upper armouring too.
The Superfeet do lack a bit of arch support but suit a lot of people.
Again we come back to how much we actually need support. The human foot has evolved over most of its working history to be used without shoes, and without shoes you have no "arch support". Arches don't typically fall down just for the sake of it: clearly there is the problem of the fallen arch, but that's a problem and not a general condition caused by walking around without "arch support".
I'm not coming to any conclusions, just asking questions... (i.e., I don't know to what extent "arch support" is genuinely useful, or like the ankle support we've been chanting about for years something that actually isn't nearly as necessary for most of us as seems to be widely assumed).
Or maybe carrying less weight on your feet, which gives them less work to do. It's possible that something a bit less chunky than your Power matics will make life rather less tiring, with a pair of good off-road shoes coming in at around half the weight (or less, if you fo for something like Inov8 Roclites).
There is the temptation to look at your past sprains and tell yourself you need more ankle support and big chunky boots, but arguably the best ankle support for most people comes from letting your body do it as it's evolved to do (and I'm speaking as someone who's had 3 ankle sprains worthy of crutches in the past). Sprains tend to stiffen ankles in the long term more than weaken them IME, and my past sparains have never been an issue in lighter footwear. In other words, I think prop them up if they've just been damaged, rather than as "preventative maintenance" which actually prevents them moving naturally and building up normally.