This question applies to both rules in ReHIPS Control Center on Programs tab in Settings and rules in RulesManager. For example you zealously examine each and every Windows update disabling any one that has telemetry features. Then you obviously don't need any telemetry rules in ReHIPS. But should you delete these rules? If not, what to do with them?
The best way is to leave them, but set to Blocked. Why? Because if you delete these rules, they'll be most likely installed again the next time you install rules or merge with newer pack of initial rules bundled with ReHIPS. If you intend to support the rules entirely by yourself and delete the unneeded rules from both Programs tab and RulesManager you'll be fine. But if you intend to merge your pack of rules with newer ReHIPS initial rules (when new ReHIPS version is released), you better leave them and set to Block. This way they won't be installed again or overwritten during merging. Besides who knows, maybe later you'll change your mind or accidentally miss some telemetry update. And ReHIPS will be there for you blocking all these processes and letting you think again.
Will auto-cleaning of obsolete rules will be implemented?
Yes, it's in our TODO list. But not sure of when exactly. Maybe in the next 2.5.0 release, maybe in the one after it.