Mistake in "Restrict possible usernames"?

JavaScript
#1

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)?

#2

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

#3

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