That is a remarkably naive view of Polish bureaucracy. If the person has such a case, then he should progress it through the Polish courts and onwards.
Beyond naive. If the person had a plausible case at all, they'd get on with it, file the court papers and win, in a stellar display of judicial expertise, rather than grumbling on here. It's on a par with those 'freemen on the land' people, or that guy who used to post here (remember him) who was convinced that Lech Wałęsa is still the legal president of Poland. Basically, it comes across as a rather strange delusion.
a huge amount of background checks are conducted regardless if it's by descent or through naturalisation,
There are many factors that would disqualify someone from claiming citizenship. You really do have to have every bit of paper in order, and if anything turns up during a claim (whether by descent or naturalisation) that otherwise the state (especially the tax office etc) had previously overlooked, Pandora's Box is opened and all sorts of problems ensue, fines, bailiffs, airport issues anywhere in Schengen etc. I've actually seen this happen to someone from Canada who was claiming citizenship (by descent, as it happens).
However, people who are attracted to minors shouldn't be granted Polish citizenship IMHO.
In my opinion too. However the immigration and repatriation authorities are not mind readers - how would they know who is attracted to whom, unless there had been a conviction for something? They deal in concrete facts - the most concrete of all being a very clean record re. tax, zus, and any time spent within Poland as well (of course) the possession of full and correct documentation to back up the claim. If a document is missing, they are not bound to search sealed archives for old paperwork that may not even be there and unseal the state archive before the legal date for that just for someone's convenience.