Adding to this, I highly recommend works from nulut[0] and niki[1].
Is there any examples of songs out there going the opposite way, trying to use something like Vocaloid to make the voice and singing as realistic and human-like as possible?
Most vocaloid definitely leans into the robotic quality.
It's also not particularly humanoid, just closer than most vocaloids I've heard. Going off of my memory of the song, it's more the intonation then the timbre that stuck out as being more realistic.
I'm afraid I'm not willing to listen through the song currently, I usually dredge up some stuff I'm not wanting to deal with right now when I listen to this artists music.