Though presumably that was done to save on production costs, not necessarily to facilitate an operator retrofitting a different engine.
Production cost savings would certainly be another advantage but the universal pylon / engine installation feature was specifically requested by potential customers during the aircraft definition phase - particularly lessors - to facilitate engine swaps. The reasoning was that once all engines were on some form of PBH programme, engine owners/lessors could compete for business on any 787 airframe over the years and, when an aircraft was being prepared for secondary lease, it could be fitted with engines to match those in the rest of the new lessee's fleet.
When Ethiopian took some of the terrible teens, they considered swapping Trents for GenX but decided against it in the end. If the Trent 1000's woes continue, swaps could happen.