There isn't a correct plural for 'octopus' because it's a Greek word filtered into English by way of Latin and so you can make a reasonable argument for basical

There isn't a correct plural for 'octopus' because it's a Greek word filtered into English by way of Latin and so you can make a reasonable argument for basically any option. If language evolution followed strict deterministic rules, then it probably would be "octopodes", but that's not the case - language changes and grows in all sorts of different ways and words become valid despite their "pedigree". As your link says, "sources differ on which plurals are acceptable"; there's no single correct option and basically all of the suggested ones are in reasonably-common usage.