This is an informational post for anyone who finds this and is experiencing the same problem.
The problem: I am using iTerm2 on my mac as my primary terminal and whenever i run
react-native run-ios the default macOS terminal pops up its instance of metro builder.
The solution: change where your mac opens .command files (thats how the builder is launched) through the “get info” panel and hit “change all” to apply to all .command files
Just an informational post for people developing in react Native on a mac using a nonstandard terminal appliocation!