The logic in not counting a WP for -1 is the same, I guess, as the logic in counting a double for -1 the same as a single. Even tho the offense gains a base or bases on a WP. If there is no advance, it's not scored as a WP, so something bad always happens on a WP, BTW.

But an HBP, intentional or not, has exactly the same net effect as a walk.

Up on a DH day? Nah, nothing special. Just time for a pee break.