Looking at 2019 passenger statistics for the big 3:
JFK[1] = 62.6 MM
LGA[2] = 31.1 MM
EWR[3] = 46.3 MM
Total = 140.0 MM
Equivalent 2019 metric for SEA[4] puts it at 51.8 MM.
So as a ballpark measure, greater NYC process 3x more than SEA.
The CDC[5] reports ~13k cases in WA, whereas NY alone is at ~267k cases; add another ~102k for nearby NJ.
Extending the benefit of the doubt, that's ~20x positive incident for 3x flight activity. Even if we pretend that WA is under-reporting by a factor of 2, and half of NY cases are false positive, the argument still falls flat on its face...keep in mind, NJ isn't even being accounted for in this thought experiment.
[1] https://www.panynj.gov/content/dam/airports/statistics/stati...
[2] https://www.panynj.gov/content/dam/airports/statistics/stati...
[3] https://www.panynj.gov/content/dam/airports/statistics/stati...