As i said many times, with enough paranoia and poorly disguised imperial ambition, a country can claim ridiculous amounts of territory under "security concerns", and do it cascading waves, as defending the further distant conquests could really use also securing the territories next to them, and so on.
By that logic Poland could have "security concerns" to grab everything between the Pyrenees and Ural, and so do all the other countries between France and Russia.
Obviously it's impossible for all of them to fulfill their "security concerns" the way Russian imperialists think they have a right to, so we're gonna have to stick with boring old system of westphalian sovereignty, internationally recognized borders and so on.
Likewise, China could build one hell of an empire by that logic, and USA could grab Mexico and Canada, because why the hell not, long border hard to defend, nuff said.
It's a completely ridiculous proposition of establishing an international order, meant specifically to excuse the conquests which Russia wants to do to begin with.
If Russia's neighbors were to apply the same standard to Russia and its puppet states, there would be nothing left of Russia.
And Russia only dares to propose such a thing because it is absolutely, legitimately, 100% certain that the West has dozens of reasons to not turn this logic around on them.
I've heard a theory that this is the only reason why Navalny is still alive.
In case the elites need an emergency plan to back down and make deals with the West, he could be the "face" for those deals.