I can confirm this, and I can also confirm the last two on the fourth board, Frost, are RNG-heavy. 
Standard practise for PW.
Make it expensive to try, make it random enough that some people get it fast.
Make it unlikely enough that the majority will have to spend large amounts to actually get there.
"I'm sure it's not THAT hard, <name> got it in like 2 tries!"
A few hundred attempts, and in PWI's case probably a lot of money later...
"Failed again!?"
