I would like to make the statement that magic is just technology not yet understood
DLSS has several "hidden" costs, so it's no free lunch. For example, NVIDIA had to gather masses of training data, which was probably costly. More relevant for us, however, is that DF has shown that the use of lower wuality textures impacts their relative visual quality after DLSS, and further some other things in the IQ aren't quite up to original native 4K. That said, it is amazing technology and completely makes the trade-offs worthwhile imo.
The DF video looked at the problem using an estimate of a much smaller chip than what T239 is. The chip they compared against (RTX2060) has 110 TOPS , which rendered DLSS using an estimated 1.8 ms, while the Drake chip could be somewhere in the range of 50-80 TOPS -- e.g. compare
here with the Jetson NX 8GB, which has 32 Tensor cores at 765 MHz for a total of 70 TOPS. Dividing by 2 and multiplying by 1.5 (1536 vs. 1024 CUDA cores means 1.5x SM advantages and half the tensor cores per SM compared with automotive devices), we get 52.5 TOPS, or about half of what RTX 2060 produces. Note that these clock estimates of 765 MHz might be low for Switch 2 docked, since there is a 1.125 GHz profile floating out there. This would give 77 TOPS if it is the actual frequency. Either way, with half the TOPS you would expect DLSS to be achievable in about 4 ms, or 1/4 of the frame time at 60 fps. This leaves 3/4 of the frame to render a 720p image, which sounds like a workable scenario considering the drop in required native IQ. For 30 fps games, you have 7/8 of the frame time left, which is almost 90% of the rendering time, so it's definitely very useful there.
Another thing is that the 20 series does not have is overlapped ALU/tensor execution. I don't know if this is possible with the Switch form factor due to potentially extra heat, or if it is practical anywhere else even, but if it is then the DLSS cost would be overlapped and be reduced to a small overhead. But let's stick to the first discussion without going into hypotheticals too much