I think you are missing what I am trying to say. Let me rephrase it.
Tyres are a real pain. PERIOD.
Doing any tyre is hard. 20" 24" 26" etc. It isnt something that you can set up to do in small volume in your garage like most other bike parts.
If someone asked us to do 22" rims or forks or frames or spokes it really wouldnt be a huge problem. We might lose money on it but we could do it.
When it comes to tyres there are practicalities of dealing with the factories that make them. They have huge production lines set up and they have machines set to each size of tyre that they like to leave set to those sizes so that they are consistant.
There are two basic tyre assembly machines/jigs and the basic ones make basic tyres and the fancy ones make fancy tyres.
It was hard getting the fancy machine for 20" and cheaper tyres are still made on the basic machine.
My opinion... is that getting the tyre manufacturers to set up fancy machines for 22" is going to be very hard. They will reason that people will either buy 20" or 22" and that there will be no net change to their sales volume, and these people dont listen to Fugazi.
I keep harping back to it, but the 29" situation is a good guide. 29" tyres can be assembled (this is prior to moulding the shape) on the same machine as a 700c road tyre. So they already have everything set up for the beads and assembly. All you need is a new mold and boom, done. MTB is also a massive market and there is way more competition between tyre making factories. Yet it still took a long time to get going...
I mention doing all the other sizes because I am a big believer in experimentation. I wasnt putting it up as an extreme example, I would genuinely like to do it. But if the 20" tyres are beautifully made then they will seem better than the 21" prototypes and that would skew the results. Much in engineering is how it is for stupid reasons and it irks me. Road bikes use 700c wheels because the UCI makes it mandatory. Can you imagine how much bikes would have advanced in the last 100 years if riders had been free to ride anything? Would we now be seeing fully suspended 20" wheeled recumbents competing against Graham Obree inspired uprights and fully faired Lotus bikes by Mike Burrows in the Tour de France? Might make for a much more interesting tour when one bike excels on the flat and another is better uphill and yet another downhill.
As I say, I love my 24" and I would love to do more 24" tyres, and I would love to try 22", but I am afraid that the deck is stacked against 22" in a way that it isn't against 24" and until I actually ride one (and more than a couple of older legends try it), I also worry that 22" is equally as likely to be the worst of both worlds as it is to be the Goldilocks zone...
G.