This crossed my mind and maybe there could be a bit of mischievous, skulduggery at work here. Of course, it could just as well be a terrible, deluded vocalist at work.
Using Variaudio, in Cubase, you can fine tune pitchy notes and play with the vibrato speeds and slides. The results are very good with few artefacts (if any) if used sparingly.
Although, I haven't tried it in anger. you can also do some reverse engineering and turn an excellent vocal performance into a train crash, sounding very much like the OP video.
Experiment, or not. To me, with an over the top vocal fail and terrible, amateur, student acting from all involved, including nods to Kate Bush and Sharon Stone from the top turn, it's all one big Urine take.
Quite frankly, I can't believe I listened to it all the way through.