Some of the chemistry is discussed in this thread:
My summary (it may not be completely right):
HQ selectively develops the more exposed areas as its semiquinone oxidation products are also developers, possibly this would imply that the fog is developed less.Organic amines make HQ active at pH 8.8-9, lower than the pH required without them.At higher pH than 10 benzotriazole is the preferred restrainer with PQ developer.
I have a couple of old films (10 yrs) to develop, will make up some Ilford ID-62 universal developer and try that. In absence of organic amines use of carbonate gives high pH and some benzotriazole is preferred.