They do keep updating the power delivery specs, which means you have to make sure you use a cable rated for the power delivery required.
"USB Power Delivery offers the following features:
Increased power levels from existing USB standards up to 240W.
New 28V, 36V, and 48V fixed voltages enable up to 140W, 180W and 240W power levels, respectively.
An adjustable voltage supply mode allows the device being powered an ability to request intermediate voltages between 15V and up to the maximum available fixed voltage of the charger."