Mistake in "Restrict possible usernames"?

Hello.

I was checking the solutions given at freeCodeCamp Challenge Guide: Restrict Possible Usernames
and the second solution looks incomplete to me:

let username = "JackOfAllTrades";
const userCheck = /^[a-z]([0-9]{2,}|[a-z]+\d*)$/i;
let result = userCheck.test(username);

Shouldn’t the second part of the regex have one more [a-z] group for it not to match the case in which the string has only one initial letter followed by no numbers (which is not accepted)?

this are the two possibilities after the first [a-z]
it’s [a-z] followed by ( [0-9]{2,} OR [a-z]+\d*)

I understand know, I hadn’t notice the parentheses.
Thanks.