Originally, I used to think that Trunks could just not know everything. There's nothing that would make one believe that all of the events (regarding the cyborgs) in the "main timeline" could not have happened in Trunks's timeline. Trunks said that Goku's heart virus kicked in before he even got to fight #17 and 18 -- well, it did. The heart virus kicked in while he was in a fight with #19, so that's not contradictory to the story. Then, Trunks said that #17 and 18 killed everyone except for Gohan. That could have still happened, we just didn't get to see that part. Trunks said that Dr. Gero was killed by #17 and that actually did happen.
Trunks was a baby and was only going by information that Gohan and his mom (I guess) told him, so how would he know about #16's, 19's, or 20's existence? So I always thought that Trunks could very-well be wrong and that the only differences were caused by him and Cell traveling back in time and there was no ripple effect that affected events that they shouldn't have interfered with (such as the battle against the cyborgs).
However, I've changed my stance on Dragon Ball. I've realized that when Trunks says it, it is the author's direct command to us that we are to believe that the events have changed. So, that's what I have to go by now. His words trump whatever deep-diving theory that I -- or anyone else -- can come up with.
So, I don't think Trunks ever specifically mentioned that Gero didn't turn himself into a cyborg, but we are told that #19 nor 20 existed in Trunks's timeline, so I'd say the answer to this question is no.