It's not a simple bolt, you know. It also has a spring relief valve built into it.
I wonder how much quality control inspection went into that $4 bolt? What do you suppose the relief pressure is on those?
I believe the bolt head was purposely left small so people wouldn't put the normal torque used on a 17 mm bolt while installing the oil filter.
A stripped bolt head is annoying. But, not too difficult to repair. A stripped engine case is
$$$$ More expensive than the entire oil filter assembly.
Cheers,