That is true some times. Other times, they are serious.
Exactly what I said. Sometimes they hope the producer/director
will see their picture and think, "Wow. I need this person in my
movie!"
In small productions, the filmmaker stick closer to their vision than high budget productions that are locked down by shooting schedules and insurance bonds.
It shouldn't surprise you that most actors do not think of all
that when they send in their resume. They are hoping only
to catch your attention - not considering your shooting
schedules and insurance bonds.
I get cover letters from dudes who say they have all the stage fighting experience and are tall enough to play a cyborg role. So, they are not blindly shooting out a submission.
You say this is limited to men. How often have you sent out a
casting notice for men only? Did you get no women at all thinking
they could play the parts?
The production we're doing is creating an Amazon civilization on another world where women evolved physically superior to men and how that forms their civilization tens of thousands of years later. So, there will be no deviating like Hollywood. We just need to lock down one final role.
Again - actors are not taking all your production needs into consideration
when they send in a resume. You know them, other filmmakers know
them, but you specifically asked why men send in resumes for female
roles. And that is your answer.
Some actors hope they can change your mind with a nice cover letter and
a great picture.