Why do you feel bad for wasting their time? if clearly details were omitted, that's their loss or problem.
In a new job I absolutely hate, but I've no option but to stick it out, (poor job market as just one such hurdle) at interview stage I asked what the targets were, the employer worded it that it wasn't targeted as such; massive mistruth come end of first week when I'm then told you solve seven cases in an hour..... too late; why could that not have been said at interview when asked.
I certainly told the people 'power point' bombarding us, training us for three weeks, we certainly didn't have all the time in the world to spend with customers as they were saying, if targets were involved by the people managing us. We're now in a horrible situation where this week is going to get interesting with the past two weeks spent in a 'pre-academy' where our work wasn't ever checked!
Loads of bad stuff came out, half the training team were as brand new, same start date as us so of course this meant a pardon, do not know, when trying to find out about the employer we'd joined, I should have worried when they started banging on about 'meditation' some 4 weeks later, think I'd rather have been dumped in the deep end! total respect for companies that get people onto the systems on day one. All I feel 'formal training' of power points on how to do the job has done is create a quivering wreak against most of us.
It makes me cross to be lied to knowing I specifically asked about targets, fortunately for me the employer seems to have you on PIP as soon as possible given enough failed QA's. It's the one time I'm wanting to say, you know what I tried, and here is the proof I am not suitable for the company. I don't want to run away from the problem that I've realised a job isn't right for me.
Good luck but do suss out the job market before you leap.