OnePlus has its proprietary Dash Charge which moves the power management, and therefore the heat into the charger instead of being managed in the phone by the Qualcomm SoC.
That explains why it is less prone to generating extra heat.
Interesting the mention of USB-PD in at least two threads on this subject, something I admittedly am not familiar with.
Will look it up though.
Given the standardisation in many areas, why is this one not being implemented more widely.
Do the phone implementations offer anything fundamentally better ?