Okay mods don't like my Futurama quotes or me talking about how we treat one another on Discord; noted. Anyways, the model engine is Playhome, still made by Illusion, but not Honey Select, it has an entirely different set up to Honey Select which would be closer to Daz's style of more realist looking thought with a heavy bend towards asian characters, Playhome can skirt more to Koikatsu in feeling more anime-esque without going full anime. Blue uses Playhome because when he was first getting set up he prefer the model styles in this engine best as it most suited what he was wanting to work with.
However, Playhome does have its limitations in that the modding community doesn't really tend to like it as much as everyone uses Honey Select and other engines over Playhome leaving it under supported and hard to develop inside. Without a strong development base, it doesn't get mod support and a vicious cycle ensues. Although this brings and interesting dynamic that means that Ecchi Sensei stands out far more thanks to Playhome being under utilized, this in turn creates a fantastic uniqueness that adds to the charm of Ecchi Sensei and thus grows popularity and curb appeal.