Resorcinol is the third of the HQ isomers - for the large part it's not regarded as a 'useful' photochemical in the amateur photochemistry world, but there have been some interesting hints over the years about what Kodak (and others) were using it for in research.
I'm making a conjecture based on your observations of using PEG in experimental lith formulae - I don't think it'll do much to slow access with 'conventional' developers. Given the chain-reaction nature of lith development & the near-exhaustion state that lith developers are used in, it's simply making me wonder if it somehow is affecting the formation/ inductance/ diffusion time of the HQ derivative that does the actual developing - or that at a particular molecular weight it somehow prevents the uptake of HQ, but allows the ready uptake of HQMS/ semiquinones.
I think there may be something that's cleared in the fixer as well - MGWT FB (brighteners but not heavily ballasted, so they can be washed out) is first pass lithable, but with most of the density only kicking in as it touches the fixer - suggesting that whatever the fixer's initial reactions are (before it even gets to significantly reacting with the halides) may be having an impact.
That might be quite difficult, given that a number of modern emulsions are intended to give maximised sharpness/ granularity performance in quite solvent developers, thus are likely to have a fair amount of anti-stain agents etc incorporated.