The -copter suffix is very common in the drone community.eg quadcopter is widely accepted https://en.wikipedia.org/wiki/Quadcopter

Counterpoint: -copter is a perfectly cromulent suffix. https://en.wiktionary.org/wiki/-copter

gyrocopter, helicopter, quadcopter, hexacopter, octocopter, parcelcopter, and—most famously—

roflcopter, https://en.wiktionary.org/wiki/roflcopter#/media/File:Roflco...

They all have their own dictionary entries.

Octocopter makes perfect sense. Everyone understands immediately what it means, and that's the only purpose of language: to convey ideas. It should be clear, which this is, and concise, which this is.

Fidelity to ancient Greek is not, and should not, be a goal for English.

Blame language evolving over time rather than OP, octocopter is a widely-used term for '8 propellor drones'.

A nit pick with your post - you use the word 'ambiguous' but really this is from the latin root 'ambiguus' so we don't need the supurflous 'o' in between the two u's.

This is quite a common linguistic phonomenon, where a word is rebracketed to form a new suffix, even if it doesn't make sense with the original etymology. See also -holic (alcoholic -> workaholic), -thon (marathon -> danceathon) or -gate (Watergate -> partygate). Termed a "libfix" from liberated affix

That ship has long sailed. You’re correct, but the author isn’t the one who “named the thing” in this case, they are just using the name commonly used to describe it.

Multi-rotor drones have been called tricopters, quadcopters, hexacopters, octocopters based on their propeller counts conversationally for as long as I can remember.

There are plenty of commercial vendors who use the exact term for their expensive industrial drones.

Update: I see that in the four minutes it took for me to validate my initial inclination and post that plenty of others also had the same thought :) No need to me to belabor the point!

"Copter" is a known word, short for helicopter.

https://dictionary.cambridge.org/dictionary/english/copter