Not so much the cup getting
pushed in as the anvil is pushed
down into the compound as
the primer is seated the first time.
The legs of the anvil are sticking
up above the edge of the cup on
a new primer and seating the
primer pushes the anvil down
into the compound.
Just me- I wouldn't utilize any
used primers for any ammunition
that I was depending on to fire
reliably. Of course, many people
do and have good luck with it,
but I'll have to pass. Not worth the
minute chance of a failure to me
YMMV