Nah, level 1 is actually correct. Regardless of its etymology, octopus is an english word and should be pluralised accordingly.

To quote some youtuber I recently watched:

Hank Green?

And my axe!

I believe what he was trying to get at is that the shikimate pathway that glyphosate inhibits is also used in the bacteria and fungi that make up the gut microbiome.

Not sure what his overall point was supposed to be (or whether he had one) but that’s the “microbiome is plants” part.