I am in total agreement with you. However, you are missing the true point. They could have done so simply to emphasize the Rangers were getting even better as each battle against the Armada was getting increasingly more difficult, as Gosei himself remarked. Besides, it is inarguable that Peluso was stronger than the previous monsters sent down by Prince Vekar, Damaras, Levira and Argus. There is nothing wrong in my opinion for them to give such a title to Peluso, if only because Matacore is coming to get them and they must prove themselves again soon enough. In addition, there are different ranks among generals of the Armada. Peluso is a basal general whereas Levira, Argus and Damaras are hand-picked elites, so he is below them in the chain-of-command, more like a commander or a lieutenant than an actual general.
Hey, you do know there are seperate categories for Power Ranger villains and Sentai villains, right? Sentai villains aren't Power Ranger villains and vice versa. The "PR Villains" page is for Power Rangers villains.