FormatRolls - string or string[]?

In the video, Ben uses a string to store roll values in FormatRolls(), and iterates through it character by character in FillRolls(). I know that a single roll will only use a single character in the string, but using a string to jumble all of the rolls together seems messy vs using a string list/array (e.g. “5/X-42” vs {“5”,"/",“X”,"-",“4”,“2”}).

Is there any reason why it would be preferable to use a string instead of a string[] or string list?

I’d have thought a struct would be more efficient, but I’m coming from Java where strings are immutable and all that iterating/concatenating would give a code reviewer a conniption. But I haven’t done BowlMaster yet nor am I a C# expert so it’s not really an educated opinion.