Issue with 2013 Merge Forms

I now have 3 examples of this behavior.  Let's say you want to merge the Opportunity (orion) form with some custom form you were using prior to the upgrade.  Also say you have an onLoad event set to run some JavaScript function on both forms.  After the merge the resulting form will run the onLoad event.  However, if you remove the function from the onLoad event of the merged form, it doesn't stop being called.