I'm OK with bleeding off some gray water into the bushes "in theory", but I've seen it go very wrong in practice.
I pulled up to a perfect campsite out in the desert once. It was just the right size for our group and there was a great fire ring. Unfortunately, the last campers had dumped their gray tank and destroyed that site for weeks.
They obviously didn't scrape their plates before they washed them, so their gray water was full of pasta, veggies, proteins, etc. The puddle they left behind smelled like hell and there was a cloud of flies, rendering the site useless.
I checked back on that site before we left at the end of our weekend and then checked it again when we were in the area a month later. The site still stank and it was still a playground for the weird alien bugs that live out in the deserts once it starts to warm up.
So bleeding off some of your shower water doesn't bother me as long as you do it slowly and let it seep into the ground in one spot. But pulling the dump handle and letting everything go (especially your nasty garbage if you don't know how to do dishes) makes you a pig who doesn't deserve to camp in the wild.