The autocomplete in the search box includes both:
- the email address of the account owner, and
- the alias for the account derived from the concatenation first and last names.
As you type, the matching accounts are among the suggested autocompletions of your query. When you select an alias, its corresponding email address is inserted as the query text. So even if accounts shared with you have overlapping names, your selection becomes an unambiguous reference the the specific account you chose.