It’s not Tesonet, Proton is wholly self-owned and managed. Proton VPN was briefly sharing employees with Tesonet during initial app bringup, and that partnership is long over.
Naturally due to competition and the huge importance of privacy in this space, people still bring this up, but Proton VPN does not and never will sell or share your data with anyone.
Source: I am a Proton VPN employee.