It's an easy interpretation. Consider his motive - he's essentially trapped himself in Groundhog Day. In addition to not having a soul to keep himself in check, he's become so bored that ultimate destruction is the only thing which interests him. Consider how a complete sociopath and sadist would act upon having no consequences whatsoever... and then suddenly having it ripped away and having to deal with a real threat to his plan when the final pieces are finally in place and it backfires when he's just SO CLOSE.

I'd be pretty pissed too.

Also, creepy Flowey face. I figure if it's a foreshadowing to his identity, it may as well be a part of his final form.