Valid point definitely. I do have a couple of counter points to it.

If we were to believe the accounts by Japanese officials, they could see different colorings in the batches they sent back - some were pink, some white and some dark. I am assuming that whatever the "x part in million" threshold, it is low enough as to not be seen with naked eye. And if the Japanese officials were lying, one would assume that we would have heard from Moderna/Pfizer an counter accusation or atleast an explanation.

Second counter point, assuming that not every single scientist who has conducted examination of vaccines under microscope is doing it wrong, you would not expect them to see these contaminants so easily. I especially trust Richard Fleming due to his extensive background - and even he was finding these contaminants fairly easily. I would say for every dozen nano-lipids he was able to find some contaminant. With "x in a million" standard, I would have expected to see miles and miles (microns and microns?) of uniform nano-lipids with one contaminant.