I don't think he planned that far ahead , much less knowing he would have to use The Bat to take the bomb. In that moment he feels its better to exclude everyone from what he intends to do. We dont even know if he even thought about going all the way. The character was always portrayed as being very conflicted.
Or he could be not sure of his autopilot fix
It's not a plothole (this term is a little overused). It actually raises questions to Bruce's behavior in the movie , and if he really changed. For us the audience , and for him as a character. He doesn't even know if he will succeed.