Appreciate the regulatory insider perspective! Completely agree that we are not seeing the whole story. The issue seems unlikely to be technical, although NXI was the first time TC was the initial certification agency for a Diamond aircraft. If there's a software glitch problem down the road, it's all on them (ref: Boeing and the FAA on the 737-MAX). I can speculate how this, and perhaps subtle differences in the wording of Canada's regulations, could result in a different technical goalpost location with higher requirements.While someone at TC may be saying that they have an issue with Garmin's software development process, it is cover for something else and, in this case, likely the relationship with Diamond. ... This is why I discount the story that it is the Canadian regulatory side that initiated holding things up. Or, put another way, if they are it is because someone moved the application to the bottom of the pile for reasons that have not been explained. We are not seeing the whole story here.
That said, I would not bet against you regarding the bottleneck actually being relational, operational, or both. For the good of the Diamond owner community, let's hope they get this sorted out soon. At this point, it doesn't matter to us owners who initiated the issue. Certification appears to be the bottleneck that is now limiting Diamond's ability to provide the next round of software updates, i.e. Phase III for NXI and V15 for the DA40 G1000 legacy systems.