This is seriously overstating things.
Steve has spent years continuously optimizing his code base. It was already clean and relatively free of cruft compared to code bases of similar age.
If you are developing on something like JUCE and don't have an extensive amount of optimized assembly or AVX instructions to deal with, yeah, porting is fast. Likewise if your suite uses a common framework (ala MeldaProduction, FabFilter, uHe, etc.).
NI's code base is not clean, and they have the organizational problem of developers coming, developing a product, and then leaving, orphaning the code base. Brian Clevinger is doing his own thing now with Rhizomatic, so good luck every seeing Absynth native. But NI has maintained active development of Kontakt because it is their cash cow, and thus their first native release. But Reaktor? Massive? Massive X? Nowhere in sight.
Further, like many developers, they have the added problem of VST3, which is a royal PITA to get right. Since Steinberg is trying to pull the rug out from all native VST2 development on M1, many larger developers like NI don't want to risk the potential lawsuits. They also have no choice but to push out native VST3s, since Cubase 12 does not support native VST2s.
So there are a lot of economic and technical pressures at work that you have to take into account.