You are misremembering some of the scenes where people who said they didn't know Toby would write down their complaints and they later went to redact them.
For instance, Kelly. She did say she thought she was talking to a friend and then afterwards realized Toby had written it down as a complaint then says she wants it redacted. Lines here (source: http://www.officequotes.net/no2-21.php):
Kelly: I didn't file a complaint. I was just talking.
Toby: To your HR representative.
Kelly: To my friend, I thought. I want that withdrawn.
And the other main redacted complaints are regarding complaints against Dwight, which are clearly complaints Angela had about Dwight that were redacted later once she started her relationship with Dwight.
Michael: Oh, ok. There were a bunch of complaints about Dwight that were put in the redacted file about six months ago.
Dwight: Whoa.. wha... wait. If someone has a problem with me, why would they withdraw it six months ago?
Pam: [notices Angela's intense concern] Um... let's move on. I volunteer. Did anyone have a problem with me?
And last there were complaints about Pam that Jim had made that he had later redacted which do actually follow in line with your question about people redacting if they didn't think Toby wrote their complaints down.
Jim: No, Pam.
Pam: [looks at to Jim] I am. [looks at Angela] It's about the Save The Date.
Jim: Pam, it wasn't her.
Jim: I'm the one who complained about you.
Jim: I... I didn't know that Toby was gonna write it down. [the camera flashes] I was just venting.
Michael: [off camera] Okay, good. Check that out.
Jim: You know, it was one day.
Michael: [off camera] That's terrible.
Jim: And I took it right back. It was like...
I see two possible scenarios. Either:
Jim is lying that he was just venting and didn't know Toby would write it down.
(per a comment @BCdotWeb made) He was truly just venting and Toby possibly followed up with Jim about his complaints about the wedding planning and Jim told him to just forget it. We don't really have any evidence for either possibility.
I think any answers will just be pure speculation since there isn't any evidence pointing either way.