There's a circular logic in your claim. You claim they aren't planning to leave, and therefore it is not leverage. But the point of that is to exactly affect the plan to leave, which is not set in stone, obviously. The fact that they aren't leaving right now doesn't guarantee they won't leave in the future.
I think you are confusing consistent logic for circular logic. Putin never plans to hand back eastern Ukraine, why would he care about something that affects russia only if it does? They are not planning for failure.
The u.s. and Canada have a demilitarized border. This would be bad for the u.s. if we went to war with Canada. However, we don't plan to go to war with Canada, so we aren't basing our decisions on that outcome.
There are certainly things that may make Putin and more specifically Russia (which can also let go of Putin) let go of eastern Ukraine. In fact, there's a spectrum of such things from nicely asking, through sanctions and military resistance, all the way up to a second front opening on the border with China or nukes flying. The plan (whatever it is) has a line drawn somewhere on that spectrum, which signifies it is time to let go. And every new bit of military equipment, fines, sanctions is pushing it slowly toward that line.
Your claim is essentially there's no line, or that there is not a spectrum or that that line is beyond any economic measures. But there's no proof of that, so the logic in your "proof" is circular because your proof predicates on you knowing exactly where the line is (or isn't), when the location of the line is the thing to be proven.
I'm not saying there is no line to get Russia out of Ukraine. Anything is possible.
I am saying that it unlikely to be reached and my personal opinion is we are moving further from it not closer.
I'm also saying that Russia is not making decisions as if it will be crossed. They are doing the exact opposite, making decisions assuming that they will not be forced out and will not get the reserves back.
I don't think they would realistically get the foreign reserves back even if they left, so that isn't much of an incentive.
The US and EU have to much politically at stake to hand them back, even if they leave. It would be seen as letting Russia get away without consequences for the invasion.
Time will prove one of us wrong. In 5 years Russia will either be occupying Eastern Ukraine or not. They will either have control of the foreign reserves back or not.
