Yes but the crucial difference here is that Russia was unofficially sending tens of thousands of it's troops to fight in Donbas from shortly after the Donetsk and Lugansk uprisings began. It was essentially a proxy war between Russia and Ukraine between 2014 and February 2022, much like how it was Chinese troops doing the fighting on the ground in Korea after the initial battles.
Any private individuals from any number of countries who've volunteered to fight for Ukraine is not the same thing as a neighbouring nation sending it's armed forces into a country to fight and claiming that they're all just 'on leave' from the Russian armed forces and decided to fight in Donbas on their holidays and took their tanks and rifles with them, not to mention those who were actually in Russian uniform, or issued medals for action upon return.