Unexpected index of Unicode subscript `char` in `string`?

A little relevant to this topic but I’d like to know is there a particular reason for findfirst to not return all the indices a char occupies when it has multiple code units?

julia> findfirst("α", "α1")
1:1

The reason I ask this is that I want to efficiently locate a char inside a string no matter how many code units it contains. I know I can definitely do something like this though:

findfirst("α", "α1")[1] : ncodeunits("α")
1:2

Thank you!