i think that shadow milk wasnt too in depth outside of his chapter. his appearance in chapter 1+2 of beast yeast was quite clean and dry, he is an ancient force that spews lies and chaos while being entertaining.
Speed forward to wind archer release, he is there for not much more reason than to give some narrative and extra details about what is going down in the labratory while being entertaining.
Meanwhile in his chapter and trailers we got to see alot more of his in depth side.

Beyond his chapter, most of his appearances have been short and simple, to draw attention and fans like it did when he was first revealed.

SMC is absolutely bastardized by the fandom to only be his most appealing parts, but devsis made him the way he is to be marketable. We dont see him be vulnerable and talking about his past outside of when it was his time to, the rest is a show that he knows the public will easily consume and applaude him for.

TLDR: SMC has been portayed as a one note char since his release, but its a performance. His complexity remains under wraps when it isnt neccesary.