Fair replies. The efficiency loss for 3* isn’t as painful, and I can definitely see a reason for a new player to want that first 4* up ASAP, even if only to 3/60. So it’s probably best to clearly preface this piece to ID your target audience.
Power leveling in 7DD et al. involves banking hundreds of feeders and food in the TCs, hoarding all the Trainer cards in inventory. Then when you pull that new HotM, you can then pull all those feeders, using them first and saving the Trainers to last, to save food. How do you get so much food, you may ask. Again, using your training camps. TC20 is a great food store; when you shift recruits from TC20 to TC11, you net quite a lot of food.
But that technique is for someone for whom adding another middling-quality 5* doesn’t matter, and you’d rather hold the 4* mats for a top-tier event hero or HotM.