Just because an aircraft is a recent type does not mean that a sim for that aircraft will be Level D; a sim for an older aircraft can also conceivably be Level D.
As noted above, the Level of the training device is related to the fidelity of the simulation and the degree to which it has been validated, not the base aircraft. You could conceivably have a Level D Sopwith Camel sim if you had the necessary flight test data available and built the sim to the right standards.
Similarly, there are times when it isn't economically justified to qualify a modern sim to the full rigour of Level D. Thus you can have a Level C device, say, for a completely modern aircraft; you can even have a mix of Levels for the same aircraft, if a training centre elects to buy a couple of (expensive) FFS Level D devices, and a couple of (less expensive) fixed base devices qualified to a lower level, using the latter for some parts of their syllabus.
One thing to bear in mind is that there are things which can make the sim better which are not covered by the Level rating; two sims, both to 'Level D', may have rather different graphics quality. Especially if they were originally qualified at different times, where the details of the qualification requirements have changed. The same also applies to aircraft characteristics and motion fidelity. The rules have changed over the years.
(It's much the same as for aircraft certification: what was certifiable to Part 25 20 years ago may not be certifiable today, but both and old and new aircraft are considered to be 'equivalent' Part 25 certified aircraft)
Generally the sims are built at the factory and tested, then disassembled and transported to the site, reassembled there, and extensively tested; it can take many months to get a sim up and running. With a 'repeat' order they may skip the factory assembly stage, and just assume it's going to go together on site, but I suspect that's rarely done.