Restricting the word "insects" to hexapods is a modern convention that does not have any basis in etymology.

Aristotle used the word "insects" for all terrestrial arthropods and this was followed for millennia until the last two centuries when someone preferred to use "Insecta" instead of "Hexapoda", without giving any reason for this, and others followed this taxonomy.

Even so, the exact extent of the term "insects" varies between biologists, because some do not include all wingless hexapods under "insects".

In an informal discussion, I do not see any mistake in using the word "insects" with its original meaning from Aristotle, which is also the meaning that can be encountered in a lot of old books. For unambiguous animal classification, the word "hexapods" is preferable.

But they are arthropods.