Is this cable in question a USB 3.1 cable? A bypass capacitor is required for USB 3.1 cables but not USB 2.0.
As to why this is affecting things, that’s a question for Samsung. I have no idea what kind of magic charging algorithm they’ve implemented in their phones, and any fast or not charging decision is up to them.
Qualcomm QuickCharge 4 is based on USB Type-C and USB Power Delivery 3.0, with a bunch of optional features turned on such as Programmable Power Supply.
So the core of QC4 should be compatible with every other USB Type-C and PD implementation out there, including on PCs. What continues to be problematic is that some variants…