I have a P226R I bought a few months ago. Instead of a "V," mine has a "U." I think it's just a cutout section to allow free movement of the barrel while firing (when the muzzle tips upward slightly during empty round ejection and reload) and also when removing and reinserting the barrel during cleaning.
Nothing to worry about.
One other thought occurred to me, but I haven't convinced myself one way or the other.
Some gun parts have been modified over the years to reduce stresses. For example, the op rod in an old M1 Garand rifle now has a cutout very similar to what we're seeing on our Sigs. It used to be just a solid, straight section, but now has a notch in it, like the "U" I described above on my Sig. It was intended as a stress reduction measure after cracking was detected. Don't really think it's the case for our Sigs as I don't see much stress in that area, but I thought I'd mention it anyway.
Just get out and enjoy your Sig. It's a great gun.