No, it is not (as tightly and modern age related to the PD2.0 and PD3.0 protocol specifications). In addition, technical facts are telling us that by itself BQ24715 supports input of 6-24V in order to charge 2S or 3S Li-ion batteries. But here it is mostly about getting/working under DC18V-20V range as (and if) PD protocol properly triggered from the used PD 20V power supply that provides reliable 3.25A (or more) at his related USB-PD 20V output port.
P.S. Also and if you open and “read” carefully above linked product page you will notice 20AWG “number” as well. Actually just referring toward designs with the DC 4.0mm×1.7mm connectors, as standard ampacity of a 20AWG copper wire is probably around 5.0A and therefore should be considered as a minimum (in order to avoid additional heat that will be produced, although it comes free of charge 
, yet only when and if covered by the RMA and especially if the used USB-C to USB-C cable was not the USB-IF certified one, and even if up to the 20V/3A USB-IF certified only) to be used with the Librem 14, considered even before any other type of USB-C cable intended to be connected/used as a power delivery one.