Not knowing th actuall cut is a good thing. We don't need people debating how good an engineer are you if the question needs to be legally answered. This also removes liability from NCEES and others.
Keep in mind you need to pass 2 tests. The AM and PM separately.
Likely, each test cut score is typically mid to high 50's in percentage. So, thats probably 22 to 24 out of 40 questions.
They aim for 70%, then my guess is they find out why a larger percentage of people didn't get this answer right, then find a legitmate or plausible reason. Then the lower the bar by that question. Or chaulk up a few expert bonus qeustions built in the test. You get that qeustion right, it onlty helps you even more.
For my test, there was nothing but mainstream elementary topic questions. I would think it would be hard for them to find that many questions to throw out or disqualify. I can think of maybe 2 or 3 questions that I knew, but had a quirky twist to them to distract you. however, they were still elementary topic questions. They just tricked you into thinking you needed more things than you did. Like to whether you knew to not include a value for a process because it was only valid for start-up for example.