Because you’re learning a whole new aircraft and a whole new FOM. And you are going to be expected to perform to standard, no matter how long it’s been since you’ve been in the cockpit. Also, your checkride is going to largely consist of decision making. Here’s an abnormal situation, captain. What are you going to do? Okay... that decision you just made... is it within FOM? Are you... SURE? Didn’t you know you could have just fixed the problem by turning this system on?

You have a brain fart and confuse the last company’s FOM for the current one. Honest mistake, could happen to anyone, especially under duress. But guess what? Here’s your disapproval, try again next week.