From an old e-mail I exchanged with him, the suit has a waterproof liner, but the main zipper isn't a waterproof zipper. From the pictures of the zipper arrangement, it looks like a stitch, and probably has the same potential for wet crotch, but otherwise keeps the rain out.
From my understanding of "waterproofing" garments, any zippered vent that is stitched into the fabric and allows air flow past the waterproof membrane has a chance to leak through the stitching. It is impossible to seal those stitches with traditional seam tape, so you aren't going to find a more expensive process like seam welding on a low cost jacket. You can seal those stitches with a liquid seam sealant, but no company is going to do it themselves because it is very time intensive.
Olympia AST's will leak at the vent-pockets for this reason, as well as the rear vents and the arm vents. I would imagine the phantom suffers the same fault.
At least the guy behind Teiz motorsports is honest about what his product can't do.