No, actually. All the single-character options to the mysql command can be "nestled" with their arguments (e.g, -hhostname), and doing so is in fact mandatory for -p.
If that gnaws at your conscience, you can use the more verbose form:
mysql --host=mysql.example.com --user=username --password=password dbname < outfile.sql
But that's just more typing for no real benefit.