Apologies for the delay in response. I can certainly see arguments for both whitelisting (explicitly specify VMDK to backup) and blacklisting (explicitly specify VMDK to ignore). I don't recall the reasoning but probably due to feedback/demand, the "include list" was implemented. I don't have much cycles these days to keep up with the various requests for ghettoVCB, the code is 100% OSS on Github and folks have been adding their own contributions/features based on their requirements. You're more than welcome to implement and share that update on Github so that others can benefit.
Best of luck