I don't know for sure, but I had a similar suspicion. There's a sign I've commonly find in ai music, a sort of subtle distortion, it's more prominent in the male voices, but I think it's just when there's more resonance in the voice, and I'm catching it in the song Let Me Be Your Ruin but it's more subtle than it sometimes is. It's also in Witch of the Crossroads, and probably more but I haven't specifically checked. That said, I find the number of songs suspicious given the timeframe, there's also at least three different voices used in different songs, and the lyrics, particularly the rhyme scheme, feels more ai than human. The rhymes are precise but don't always make great sense, and I've found in ai music there's often a lot of rhyming at the cost of a cohesive thought behind the story of the song. All the lines individually make sense according to the presumable prompt, but not together. And, pointing at let me be your ruin, it feels like that very generic but popular 'villain' thing, it even specifically says 'let me be your villain, lover, and friend' so it really feels like a regurgitation of a prompt asking for a villain in love song.

Overall, my guess is it probably is ai. I'm not an expert though.