There's a third answer, that these numbers aren't statistics -- "drops" is an opinion, not a fact, based on the definition and judgment of the one assigning the number. So for example
here's the drop numbers by QB from Sportingcharts (I believe uses STATS, LLC data) that shows a more similar drops result for Keenum & Goff.
Also the sample sizes are really small so the margin of error has a huge effect -- e.g., subtract or add 1 "drop" opinion from Goff's number and it swings his "drop percentage" by 1 percent either way and he probably goes from the top to bottom.
Anyway, don't want to take away from the value of the discussion too much because it's clear to all Rams fans the WRs didn't do Goff any favors.