That sounds highly unlikely, the one that came with my MBP supports everything up to Thunderbolt. But USB is ridiculously complicated, and sometimes better cables fail on shitty devices; I've seen it a few times with camera equipment where I really needed the cable that came with it because higher specced ones just didn't work.

True if they are referring to the MagSafe cable. If referring to USB C to C, they’re mistaken. The charging cable for all MacBooks does support USB 2 data rates.

The charging cables included with MacBooks do not support Thunderbolt. Just USB 2.0 data.

I do have an Apple Thunderbolt cable which supports charging (of course), but it was a separate purchase. The Thunderbolt cable looks similar but is a bit thicker, and has the Thunderbolt logo printed on the connectors at each end.

Unless you received a faulty cable, which I guess is technically possible if extremely unlikely, this is categorically untrue.

In my limited experience, USB cables do go bad. Fortunately the USB-C and A female ends take much more abuse than the cables.

It's actually not technically possible for a faulty USB-C cable to function as a (> 5V) charging cable without data, because the power delivery negotiation happens over the data connection.

For USB C-C cables PD and passive 5V (5K1 pulldown) is negotiated over a separate CC pin from the USB2 D+/- pins, so it's theoretically possible if the D+/- lines are not connected/damaged.

USB A-C cables are entirely separate, there is no CC line, only a fixed always-on Vcc pin at 5V.

Not even close to true. Remove it from the charger and use it as a data cable, works fine.

They absolutely do. I have three and use them all the time. Use case (beyond charging) to have them right in the box is that they can be used to transfer data from a previous Mac to a new one upon setup (heir to the good old "target mode" that used to turn a Mac into a USB mass storage device), or for T2/Apple Silicon to debrick the device by entering DFU mode.

Just got a fourth (shorter, different from MacBooks) one with my new iPad, it has data too, which I just used yesterday to restore the encrypted local backup from my previous iPad and perform a new local backup. I bet the cable shipped with these new iPhones is the same as with the USB-C iPad ones.