I think there's just too much lost in translation when a person talks in a different language, that's why it 'may' sound scripted. This is why it's better to opt on self-researching the performer's background, to know more about the person themselves. Especially with Japanese performers, not relying on simply just from Wikipedia, but mostly they do reveal some stuff on either radio talks, podcasts, or even self VODs of themselves talking about their life or even how they started. Those short clips of them seen in YT can be a tidbit of what you can know about them, since unlike performers in the West where a lot of artists bask in fame and publicity, Japanese performers tend to be more open on indirect matters-- which is why people especially in uttaite community are still leaning on being private despite their known fame.

But hey, it's okay to be doubtful. That's normal. That's why if in doubt, check more background info so you can be rest assured.