And, BTW, there must be hundreds of thousands of "unbalanced" H&C systems still around, so not exactly "rare" (Another Agile blooper)
I agree there will be hundreds of thousands, perhaps 300,000 of them.
That would equate to just 1.7%. Or less than 1 in 50 !
I said "pretty rare" and not "rare".
Not a blooper in any way in my opinion.