I think what upsets me most about the heap of failed logic surrounding Poland for liberals who subscribe to the Horseshoe Theory is that they don't really expend much mental energy on it. They believe that the Nazis and the Soviets were equally terrible in Poland, that both worked together to steal land from Poles, killed lots of people, and tried to erase the culture, and that they did it for basically the same reasons.
But then there's all the extra details they don't know, or don't choose to factor in when making their opinions. The Nazis, as you have broken down for us, had a very clear and published plan for the removal, extermination, and/or conversion of the entire Polish population into a German settler state. They had a very explicit plan and clear intent to take all the land from whomever they deemed subhuman. They didn't hide this, this was well-known and their views were even shared by many in Europe and the USA.
The Soviets, meanwhile were the last of the major powers to sign a non-aggression pact with Nazi Germany, but people focus on the "Secret Plans" to divide Poland as if this is proof positive that they were secretly Authoritarian Best Buddies. To me, however, if you take in the facts that 1) Germany was preparing an invasion of Poland, a country the USSR shared a border with, 2) the USSR was the last major power to sign a NAP with Germany, and 3) the territory the USSR wanted from Poland was territory Poland had taken in the Polish-Soviet War... it suggest more that the "Secret Plans" were conditions for the USSR to agree to a NAP in the first place, guaranteeing the reclamation of the territory lost. Correct me if I'm wrong, but that's all accurate to the best of my knowledge, isn't it?
Additionally, the Polish government was committing cultural genocide against Ukrainians, Belarusians, and others in the territory they had claimed. When the USSR invaded and claimed the territory, "murdering" the intelligentsia there, how can libs not consider the fact that this likely had to do with the fact that the Polish nationalists in the region were the ones purging it of non-Polish ethnic groups? You can make arguments of excesses in the executions, but to just pretend that it was all a bunch of harmless Polish liberal authors, professors, that the USSR was just trying to control everything, is really missing the point.
From what I know about the motivations and policies of the Nazis and the Soviets in Poland, the two are completely incomparable except on the most meaningless surface level. Yet, the words of collaborators apparently hold the most stock in post-Soviet history books. It's just... upsetting.
I'll confess I don't know the full details of what went down there. I definitely need to do more research.