Same experience David
I use regular zippers, no flap, and don't seal seams either in Oregon and Washington and never noticed any drips. Many times with heavy rain and wind.
However, I don't have anything directly underneath the zipper, but you should do that anyway because when you open the zipper to get in and out water will drip down there.
And my rain jacket has a regular zipper with no flap. With coil zippers the fabric of the zipper tape almost completed blocks the opening, but this is breathable fabric. There is probably a little rain getting through, but I get way more perspiration than that so it's not significant.
One time I had an annoying drip where I sewed on a velcro strip to hold the door open. That's the only thing I worry about waterproofing. Use silicone.