You're right to question it and I would suspect it is but don't listen to me, plenty more here will give you better advice on these divers....however, for me - I'd like to see the lume pips and the shape/size if the surrounding triangles....
Fuethermore, how good is the bezel to the rest of the watch?! If it does not match particularly well the it's probably been changed, and I doubt for a genuine one!
A picture of the silver triangle and the pip would also help. The texture on an original insert is matt with a grain-like appearance. The pip is slightly recessed, and there is a small black space between the edge of the top of the silver triangle and the edge of the bezel itself.
The texture of your bezel insert in question looks good, but the font is slightly off and "20" is too close to the edge.
Questionable... I agree.