Resposta do suporte da AWS (enfatize o meu):
If you setup a wildcard DNS entry for your Domain this will catch all queries where you haven't specified a record.
As example:
localhost.domain.com. A 127.0.0.1 *.domain.com. A 127.0.0.2 www.test.domain.com. A 127.0.0.3
A query for localhost.domain.com. will return the specified A Record 127.0.0.1
A query for test.domain.com. will return the wildcard record 127.0.0.2
A query for www.test.domain.com. will return the specified record 127.0.0.3This means a specified Record within your hosted Zone will always have a higher priority as a wildcard record.