I am not sure that there is any link between bad taste and hardiness. Changsha is pretty hardy but has no bad taste. Certain Poncirus hybrids have a relatively good taste without being especially frost tender. We know of much better tasting Poncirus types that are as hardy as the bad tasting ones.
It is more wise I think to look for scientific ariticles about Poncirus hardiness than to speculate about a link between taste and frost hardiness. Keys to winter hardiness are certainly winter dormancy, early flowering and sprooting combined with early stop of growth so that twigs can harden off, deciduousness, and sunken stomata in the twigs (as a reaction to quasi arid winter conditions when eath is frozen). I suppose that Poncirus has other mechanisms too as the ability to reduce humidity in its twigs and the ability to reconnect the water column in its wooden parts when ice crystals have disrupted it. Other frost hardy tree can do that.
Regarding early sprooting and early stop of growth, I have seen that Poncirus varieties differ greatly. Some will never have a second growth in late summer or autumn even when they are in a warm green house. Others flower again in autumn even when they grow outside. I suppose that winter dormancy is regulated by different independant mechanisms or genes, some that are sensitive to day length others that are sensitive to temperature. I further assume that these mechanisms are active in different varieties to a different degree so that some are mainly sensitive to temperature others also to day length. I have though no scientific information about that. I only remember an lexicon article that states that Poncirus is sensitive to day length. What I see myself is though a mixed picture.