Power Delivery ("PD") requires chips inside the cable's connectors to work. The chips provide information on the cable's capabilities. No chip, then standard voltage, standard current only.
Thunderbolt is 40 Gbit/s over two serial lanes. That's 20 billion bits per second over a single link. I'm not an expert in this field (i.e., the field of high-throughput cables) at all, but that doesn't sound very realistic to me for regular cabling. But I guess the use of copper, gold contacts(?), differential signaling, shortness of the cable (or alternatively active components), and an immense amount of shielding make it possible. These cables are quite expensive.
The cable ID is only required for the higher end of possible currents. You can still get 60W (20V, 3A) through a non e-marked cable with USB-PD, just not 100W (20V, 5A).
Thunderbolt is 40 Gbit/s over two serial lanes. That's 20 billion bits per second over a single link. I'm not an expert in this field (i.e., the field of high-throughput cables) at all, but that doesn't sound very realistic to me for regular cabling. But I guess the use of copper, gold contacts(?), differential signaling, shortness of the cable (or alternatively active components), and an immense amount of shielding make it possible. These cables are quite expensive.