The patch provided by Nick would implement the /etc/skiprbldomains behavior across all RBL configurations deployed through the "RBLs" tab of the Basic Editor under the Exim Configuration page. No changes through the Advanced Editor would be needed with Nick's patch. It'd just be a means of following Nick's post of applying the patch, running the necessary commands he posted to build out a new exim.conf, and editing /etc/skiprbldomains. Keep in mind that cPanel updates will revert the patched perl modules, meaning that if you were to ever need to re-save Exim configurations you should re-apply Nick's patch before each Exim config save to ensure the patched behavior is present.
The steps you've posted could be deployed as an *alternate* solution to Nick's patch. You've basically pulled out the changes Nick made and wrote them in a suitable instruction set for the Advanced Editor.
The only item of note I'd remind folks about with your manual deployment, though, is that you deployment would be best suited for if all of the default RBLs were *disabled* in the Basic Editor, since you are effectively adding in a custom RBL manually. If the default ones were left in, it would result in duplicate RBL configs.
In short, if your steps were used in conjunction with leaving the cPanel deployed RBL configurations on, then the whitelisted domains would appropriately skip your custom RBL acl but trip on the default RBL acl. If your steps were used in conjunction with Nick's patch, efforts would be duplicated and potentially result in a failed exim.conf build at worst and multiple DNS requests to the RBLs at best.
In short, whichever method is chosen, only one of those methods should be deployed. Both accomplish similar end goals and are completely acceptable.
At the very least I'd recommend opening a feature request at cPanel Feature Requests
for this so we can see the demand for this functionality being added to the product.