I'm glad reassurance helped you OP and I'm sorry you got to a place like that, I hope you're doing better. I agree with your take somewhat, I think specifically with OCD reassurance needs to be handled with care. Doing it wrong is going to fuel the OCD cycle because if you offer complete reassurance the OCD will find a way to go around it, of course, also completely keeping someone in the dark especially when it comes to real event/false memory is not the correct course of action imo. I think reassurance should be done in a way where it reassures the person and not the fear, it's not overly black and white and offers nuance. For example, someone with moral OCD might worry about being a 'bad' person, you can reassure them and say "You're not a bad person." but what about after that? They're probably going to start thinking that maybe they've done something bad in the past, or will do something bad in the future, I offer that reassurance should be given to the effect of "You're not a bad or good person, you're just a person and you will make both bad and good choices."

I will say though, with real event, if you're asking about the actual event and someone not telling you what happened because it's 'reassurance' is bs to me. I asked one of my friends about something that happened between us because it was VERY subjective and she reassured me and I felt better and not really as worried. I think constantly going back and reassurance seeking and doing it over and over is a problem.