vB3 is the version for which it does not work, you can just read the code of the verify function and the issue is evident. No, they do not use both the template cache; you are basically doing a string replace in the template cache in vB3.
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Since you are using a reference to the function argument ($cronimage) your branding free removal works in vB4, but not in vB3, where you are doing a string replacement looking for the string "$cronimage" into the footer template.