Talented king.
If you want to know the physics behind how Tae goes tenor when he's a baritone in full chest voice (and can briefly dip to bass range when necessary), you can train your vocal tract. Bighit actually has very good vocal coaches, you can noticeably hear an improvement in all their artist's tone and range over the years. There are vocal exercises you can do to extend your own tone and range if that's something you want to do. Tae (and Jungkook, actually but that's a discussion for a different thread) regularly extends his range, which is perfectly fine and healthy for a professional singer who's doing his work correctly. All of BTS sing with extraordinarily good production and technical skills, which again, is a testament to the talent and dedication of their vocal coaches. Hats off to Bighit, whoever you're paying for vocal coaching, don't stop.
You have to be kidding lol