Standardize the colors through the IF, and bam, you can tell at a glance what a cable is capable of.
Like resistors, except I don't think cables are likely to shrink too much in the future.
I will say, they're not alone. Look at Razer, for instance. Electric green is not exactly a part of the USB 3 standard.
If it's a cable property, then Apple can do whatever it wants with its cables. And everyone else can do what they want with theirs.
I think what we've learned throughout the years is that your color coding idea doesn't work out in practice due to an earlier comment stating that the USB-C market being bottom-feeder. There has to be an exact, rigid specification of USB-C cables that all of them should follow (i.e. USB4/TB4). Any more complicated than that like color coding results in giant scams by manufacturers, outright wrong, or impossible-to-find cables on an eCommerce search engine. I just don't want to deal with any of those anymore. It feels so much nicer right now to look up TB4 on AliExpress and be done with it, no more worrying or guessing.
I don't have any idea how thick the 19 wires have to be for USB 40Gbps (GBps?) but I imagine the answer is "not nearly that thick".
The advantage of USB 2 is that it's so simple that it's very hard to screw it up. You pretty much have to intentionally do it if you want to create a dangerous cable. Even the shittiest cable will work with the vast majority of devices (it might slightly heat up, voltage may sag at the receiving end meaning it will charge slower, but it'll somewhat work).
USB-C is significantly more complex and requires active electronics in the cable itself in some cases, and the potential for higher voltages means a faulty/recklessly-designed cable could request higher voltage from the charger and blow up whatever's connected at the other end.
And the cheap cables won't have that chip, so they'll support 60 watts.
The difference between the minimum and 100W is that the cables need to support 5 amps instead of 3. That's not much difference at all considering there are data wires too.
Supporting 240W requires a couple tiny components in the plug. That's also barely anything.
So when operating at 90W the cable only needs to be a tiny bit thicker and negligibly more expensive than a normal 15W cable.
I do not want all my USB-C cables to support the maximum 40 GBps speed (or whatever it is). That would require them to have all the 19 wires and shielding and all and again, would make them expensive and short.
And just imagine how much a 90W maximum speed 3 meter cable would cost...
I prefer having one power cable, one fast cable and then a bunch of disposable cables for general use cases.