There's interviews with his butler where the butler talks about the toothpaste and also being called into his office in order to throw out one piece of paper into a paperbasket next to the desk.
Skepticism is only worth anything if you follow it up with research and this shit is pretty easy to look into. https://www.cosmopolitan.com/uk/reports/a38743898/prince-charles-doesnt-squeeze-out-his-own-toothpaste/