As for the Airbus X extended, this plane has no wing flex built into the simulation. I understand (I could be wrong) that where a plane, like the T7 and NGX, incorporates a good wing flex model there is a high degree of difficulty (or impossibility) in making the flashing strobes stay on the wing tip. Thus, as far as I know, PMDG have elected for the less obvious strobes. Personally I think they are have made the correct decision, i.e. I prefer wing flex to bright lights, and I also enjoy the feature of ground reflection of their light effects. As I said, I could be wrong but I believe I read this explanation on another site but can't remember where.
I agree with Erek though, in that when you are inside a plane it's difficult to see the lights on the wingtips unless they light up something like clouds or fog. From outside it's a different story as Jason's great videos show. I assume that external lights on planes are designed to broadcast outward to traffic and not inward to the passengers.