Tether said that the coin reserve's destruction, which is a move not often seen in the cryptocurrency space, is in line with the Tether white paper (.PDF).
source https://www.google.com/url?rct=j&sa=t&url=https://www.zdnet.com/article/tether-sets-fire-to-500-million-usdt-cryptocurrency-coins/&ct=ga&cd=CAIyGmM2Nzk3ODA2ZWViNjVjODI6Y29tOmVuOlVT&usg=AFQjCNEVJqc7-NRtAMiiZM6Lx2_H-0AQ6Q
