Am going to give a closer to home analogy of the Russia-China relationship.
Situation 1:
I drive you to work.
I use your money to buy grocery for you.
Situation 2:
I give you the key to my car.
I buy you grocery with my money.
In
Situation 1, there is zero to nearly zero costs to me. We could be working in the same building or I may just drive a few minutes out of my way. And when the time come to buy food, I am using your money, it may take a few extra minutes, but it is still your money.
But in
Situation 2, I would be out of my car for a while, maybe even the whole day. You may pay me back with a full tank of gas, but I still do not have my car for as long as you have it. And when the time come to buy food, it is out of my budget, you may pay me back later, but it is an actual burden on me until that time of repayment.
What China is doing for Russia all this time is essentially
Situation 1 with the credit card processing, buying Russian oil, etc. But if it is true that Russia asked China for economic and military assistance, that would be cutting into China's wallet, today and tomorrow and until who knows when Russia can pay back. Considering that Russia is using Syrian fighters, what happened to the rest of the Russian Army? What if Russia even asked for Chinese troops which would mean China have to budget out Chinese blood to help Russia? Why not? The PLA have no combat experience so this would be a valuable learning experience prior to invading Taiwan. Chinese troops dying in Ukraine would definitely elevate Taiwan's morale.
China is sloooooow walking aawaaay from Russia. Neither country can admit to this story because that would be an acknowledgement to the world that Russia truly failed and that China gambled wrong. So all China can do is continuing with
Situation 1 as Xi seethe with anger behind closed doors because the Russian military failed him.