Ukrainians will not allow the exhumations for a very simple reason
I'm not sure that that is the actual reason.
Personally, I think there are no bodies left there - I've said this in the past. Volyn and Galicia have been electing ultranationalist public officials since the early 90s. I wouldn't be surprised if they already "recycled" the dead bodies at some construction site.
However, that's just my personal conspiracist take.
In their public discourse amongst themselves, where they have less fear of being watched, still nobody ever mentions "fear of being embarrassed". Perhaps they should, but they don't.
Instead, the accent is always on "what will we get, if we allow them to come and exhume?".
It's what I wrote before, in regards to Ukrainians showing their true face by trying to engage in a "trade" over corpses.
They think, in their lumpen brain: "We let the Lyakhs take their bodies - they promise to help us get into the EU. Quid pro quo."
They don't understand how this makes them be in the same club as Hamas or Boko Haram. You know, as Pawian says - they need some more decades to mature as a state.
They see that Hezbollah can trade the corpse of a dead IDF soldier for 1,000 jihadists sitting in Israeli jails - and they think, "The Poles are also bleeding heart suckers, it would be foolish to forego asking for dividends from this trade."
Maybe they are even right... You saw what Sikorsky said - "These people have descendants... and they vote in elections. So the question is political."
That is, if it was a PO government which finally "bent" the Ukrainians to agree to the exhumations that would be a win for PO. If PO cannot achieve this, but PiS can - then it is a win for PiS. The Polish government could quietly promise the Ukrainians help in other departments, if the Ukrainians quietly agree to allow the exhumations.
So maybe their terrorist tactics are not so myopic as they seem.