I don't 100% understand what this condition implies.
What is interesting, is it is 1 coin at a time.
I forget which it is - does staking or mining reward 1 coin? I think it is mining. 1 coin per block.
So maybe he is mining so fast he is filling up his wallet / generating a lot of unnecessary traffic?
1 coin is current block reward on PoW, on PoS rewards in my wallet from 0.1 to 0.6, so a withdrawal of 1000 coins is a really heavy transaction, since it will have 1000 inputs or even more.
I looked the code and yes it seems that method writes to disk after every WalletUpdateSpent