Legally both replicascounterfeits and 3rd Party Products are unauthorised IP infringements. However, as heroic_decepticon pointed out, not all IP infringements may be in breach of the law per se (re: de minimis non curat lex). Ethically speaking, well -- that greatly depends on one's personal values and opinions (e.g. deontology, consequentialism, utilitarianism, altruism etc.)

Classification - as always - is inherently arbitrary and subjective; just like any other system of classification, e.g. biology (do non-DNA based organisms (like a virus) count as living organisms?), astronomy (when Transformers first debuted Pluto was a planet!), geology (there's no consistent difference between what counts as a continent and what is an island) and of course, toys (e.g. counting methods).

So whether an ethical difference exists between the two entirely depends on one's own values and opinions - and there is no definitive 'right' or 'wrong' answer. For the purposes of what OTCA considers tolerable and intolerable unauthorised products - as far as I can see - appears to be based on counterfeits (KOs) being classified as intolerable, and 3rd party products being classified as tolerable.

Now I'm not saying that this classification is right or wrong, nor am I saying that your classification is right or wrong. They just come from different schools of ethical thought. But for the purposes of running the board, there needs to be a defined standard. And it's ultimately the admin's role to decide what that standard is.