Usually what people want is to "make my device charge fast" - in which case the cables not implementing the spec correctly work while compliant cables would not.
Of course, there is a reason that compliance exists! Chances are you are plugging this cable into a wall-wart made in the past few years with higher tolerances than needed, and things will work out fine. Until they don't. Then you may burn out a PC USB port, or potentially I suppose catch a cheap chinese wall wart on fire.
At least that is my current understanding having spent the past few days attempting to decipher how this all works. The correct way to go about this transition to USB-C is to toss out all your USB-A chargers, buy USB-C chargers, and if you need to adapt; adapt in the USB-C -> USB-micro/mini direction vs. the USB-A -> USB-C direction.
The tldr on this is basically if you plug into a USB-A charger, you should not be able to "rapid charge" at 3A. If you are, you are out of spec and could potentially damage something you plug that cable into. Just give up on the dream of using your old chargers and expect to replace them with chargers that implement USB-C there. If you need to charge USB micro devices, invest in some USB-C -> Micro cables (or adapters) instead.
You can still rapid charge with a compliant type-C/A cable, but it needs to be negotiated through one of the other specified mechanisms (that directly talk with the other end and thus can figure out what the type-A charging side can actually provide).