Does every wheel built up with a Mavic 717 have a hop at the seam ?

If you're talking about imperfections on the braking surfaces, I own three pairs of wheels laced up with Mavic 717 rims, and the braking surfaces are machined in a lathe to be perfect.

All 4 wheels have a small flat spot right where the seam is.... as in slightly out of true. Not talking about the area on the sidewalls where they grind the weld down.

Mine are not flat at the seam, they were absolutely true when I got them. I have pounded the hell out of them so that they aren't true now but the errors still aren't at the seams.

This is called the Mavic Seam Hope. Not uncommon, don't worry about it. I have built 100's of Mavic's had some of their models have this worst than others, but it has no real effect on the wheel.

Flat spot in heigth

Yes, I have built about ten wheels with X717's (Disc & Ceramics). Nearly all of them have a flat spot on the outer diameter. I think that Mavic sands the rims a bit at that point after the welding is done (and before the anodising).

On some occasions I even have to apply a bit lower spoke tension at the four spokes around the weld to make the wheel completely true (apart from the flat-sanded spot which is around an inch wide).