I cannot say that I am seeing this. I have been experimenting all week with propping up the Nationalist China with resources from the USA.
I pumped resources into Nat-China every 15 days and they still lose to the Japanese by 1939.
Once Japan has started making inroads into Chinese territory I have been exiting as the US and looking at Nat-Chinese resources. None are short all are well over 10K. In one game before NatChina surrendered I looked and they had over 15K in supplies.
So while giving supplies to the Chinese helps slow down the Japanese progress, it doesn't stop them from failing to defend China.
I found myself hurting for resources as the US and my normal peacetime build routine was trashed since I was needing to keep the production of supplies high to feed the Nat-Chinese.
In the end I decided I would rather have my infra and IC constructions completed and start my prewar build up, than spend the extra time propping up Nat China when they are just going to cost me resources, time and energy and still surrender to the Japanese forces.