The only time “Kosher For Passover” products are readily available is in the Spring...Just Before Passover.
After that, they become out of date!
Interesting that the ancient Hebrews figured out that sometimes you gotta' give up the wheat, barley and rye!
Almost like there was some segment of the population ~ maybe the Scribes ~ who were "different", so this was a token of respect.
My understanding is that rice was not known in ancient times in the Middle East ~ so it was handled like Quinoa ~ but it got put on the 'bad list" in the Diaspora in Spain.