Probably to the person who owns it or sees it (Excluding Medical professionals)
But no, I don't think a healthy functioning penis that just has a small flattish mushroom tip would be considered a defect to a medical professional.
Like, compare it to a curved penis, some are pointed left, pointed right, curved up, curved down, etc.
Some have bigger mushroom tips than others, some smaller.
It's quite funny how genitals come in all shapes and colours