Like I said with France and the 13 colonies – no country is actually saying that or has ever said that. France didn't go "yeah, we love what you're trying to do 13 colonies and support your beliefs wholeheartedly", they went "oh cool, this will help us regain New France one day and really piss off our archrivals."
Saying "oh cool, this will help us regain New France one day and really piss off our archrivals" is still supporting them. That's my point, seperatists often rely on geopolitical rivals supporting them for ulterior motives. You can't really cleanly separate bottom-up political activism from opportunistic rivals with ulterior motives, because in practice the former will generally rely on the latter. Generally when you're fighting a civil war, you don't have the luxury of turning up your nose at offers of assistance for the sake of purity. So if your position is supporting seperatists movements except when they recieve foreign backing, you're not going to find yourself supporting many seperatists movements in practice, at least in cases where they have to fight.