Yes, often when gutters are not installed this strip of bent gal. or aluminum under a course of shingles to simply guide the water away from a doorway or deck entrance, who wants to walk through a waterfall on their way out or in ?...lol (Today 99 degrees...I DO !!!!!!!)
Ooops, almost forgot, to remove the strip, gently pry up the shingles with a flat pry bar a little at a time all the way along the drip edge length, when you have it up enough to see the nail head holding the drip edge then pry up these nails, when your done run a bead of asphalt shingle caulk (horrible black tar in a tube) right along the bottom edge of the shingles and pree the upper layer back down onto it. (WARNING.....the asphalt caulk/roofing caulk doesn't come of skin easy).
Is it common...no, 95% of builds will have some sort of overhang even if it is just 6" or a bird box to accommodate the corners.
Is it OK....no, I'd seal them up with a good quality exterior caulk. You might have to have a couple of goes at it simply because it's a big hole, unless you can get hold of some caulk filler strip, then just push that in and then top of with a good bead of caulk.
The area that the water is going down is only protected by the tyvek , if there is a tear or a nail hole or a nail for that matter then moisture will get in.