No, but the maternal grandfather is still a male ancestor. Parent said "all male ancestors had a son", which is not true. The true statement is that, for any generation of ancestors, at least one had a son.
There is an unbroken line of males having males and females having females, but not every male ancestor had a son and not every female had a daughter. Every ancestor had a father and mother, but it doesn't work in reverse.
You can tell a son that all their male ancestors had a son!
And you can tell a daughter that all their female ancestors had a daughter!
No pressure indeed!