I don't understand the question. Are you curious to know what entering "r" by itself on the command line will do under all possible circumstances, or do you you want to fix it so that entering either "r" or "R" will launch the R console?
If the latter then I think,
alias r='R'
will fix it.
Neither do I. I've never used zsh or R. But I just read the zsh manual and it says that an alias is applied first, so that's why I suggested it.
@Pat I was just curious because I didn't know the 'r' command. I'll usually run R through RStudio.