This annoyed me too. They seemed to do a lot of building up names of Transformers that MIGHT BE IMPORTANT only to have them...last one scene. Megatron's whole "I want my crew" scene was pointless since it took longer to introduce them than they actually lasted in the next scene. -.-;
I thought he explained that he couldn't talk because he didn't want to tell his daughter anything that could risk her safety in some way, so he just didn't say anything at all. I dunno, it was all hazy.
Yeah, that could have let them cut about 10 minutes from the movie. Could have just had them show up, have their names be mentioned and that be that. I felt like that entire section was trying to copy Suicide Squad for no reason.
I thought they only worded it as he couldn't say anything as if he did they would be able to track him down. Although like I said I worked a few 16 hours days (1am to 5pm) the days leading up going to see it so I might have went brain dead for a few minor plot points and just missed a line or two. It could have been that by him saying something it is then proof she is talking to him where they could then use her against him as opposed to her just talking to dead air and them not knowing for sure that she even has a way to communicate with him.