I'm feelin' your pain, but to be fair, the need for codes is not always obvious. In this case, they're covering their butt for the future replacement of your cartridge filter with a sand filter. Or for draining water out of your pool, too, right? Both of which are real future possibilities. You'll probably use that line at some point, or the next owner will. And it'll be nice to have it right at your pad, instead of trying to dig up your sewer clean out, and running a big, obnoxious hose out front.
You know how it works, without that drain line, some people would backwash anywhere, and empty their pool into the gutter (running to the local creek) in the middle of the night, to not get caught. The code is protecting your neighborhood, local waterways, etc.
Just lookin' for the silver lining for ya...