findAll() on Customer returns rows only. There is no orders field to be lazy or eager:
  Customer[id=1, name=A, email=a@example.com, tier=STANDARD]
1+N queries (4 SQL statements for 3 customers) -> [A:2, B:1, C:0]
two queries (2 SQL statements)                -> [A:2, B:1, C:0]
one LEFT JOIN, grouped by hand (1 statement)   -> [A:2, B:1, C:0]
all three strategies return identical aggregates: true