The thing I like about this argument is that, unlike most, it’s not very technical. Everybody has experience with pollen.
If you consider:
- All types of plants grow at all elevations
- Pollen can be blown hundreds of miles and ends up everywhere, including the ocean floor, caves, and mines
- Pollen fossilizes very well
…It’s pretty hard to imagine it not ending up in all flood sediments in abundance. A counter of “one time somebody found it in a lower layer” would not explain the overall pattern. You would expect disturbances or mistakes to create false data points occasionally.