As always, it is very interesting to see such large gaps in what essentially comes down to basic aerobic metabolic capacity and observe the gap within the subpopulation of the elite of the elite cyclists.
While some riders' ability to just take off is indeed the new normal, it wasn't that way 10 or even 5 years ago. Within this time frame, the peloton as a whole became more professional and competitive. Arguably the expectation then is to see gaps diminish.
If you assume that human aerobic capacity follows a normal bell curve then it's actually expected that the top few examples are extreme outliers. This is even more pronounced in the pro peloton, which itself does not follow a bell curve but is the rightmost slice of a bigger bell curve.
Think about it: if you are one sigma above the median, then 47.5% are within one sigma of you (34% worse, 13.5% better). Out of one million, there are 475,000 who are within one sigma of you.
If you are 2 sigmas above the norm, only about 16% are within one sigma. That's 160,000 individuals.
There are expected to be about 3 examples out of a million that are at least six sigmas to the right of the median. There are only 230 that are within one sigma of those (i.e above 5 sigmas).
Concretely, the standard deviation might be something like 6 mL/kg*min of vo2 max. So the farther out on the curve you get, the fewer others are within that constant amount of vo2 capacity.
In other words, we should expect the outliers to be very extreme, much more distant to their nominal peers than an average local enthusiast is from his or her neighbor.
At a race like SB, the advantage one would need over their peers to simply ride away is of course much less than the advantage that would be required to do so at most road races due to the nature of the course.