Have you tried them for privacy purposes? What are your experiences?
Here is mine. I’ve used the Visa prepaid cards. Where I live (USA) you can buy them “anonymously”. Scare quotes because sure, nothing is 100% anonymous now. But you can buy them with cash and activate them without giving a phone #. Not quite as anonymous as cash, but close. It avoids the heavy data trail of a normal CC. And you can use them sometimes where you can’t use cash.
But there’s the prob. It’s hit and miss if they work. Unfortunately, these are HUGE among scammers, so those scammer fucks poisoned the well. Some stores will flat out deny them. Other times, they work fine.
I’ve had probs at some point of sale terminals, others work OK. Ditto gas pumps. Seems to be no way to know which way it’ll go without trying. Which means you gotta have another way to pay lined up.
I haven’t tried them for online shopping yet.

I believe you are right. In your doubtfulness. In general I mean, IDK about the person you were replying to, they could be an exception.
I think at most we’d see a very few holdouts. Almost everyone will go along. As you say, using a phone already ties it to you, for most ppl. There’s a GPS track that stays in your home every night, and goes to your work every day. Fingerprinted browers that log into your accounts. A whole social graph map.
However. It’s still a backward step, IMO. Today, it is possible, VERY difficult but possible, to use a smartphone anonymously. You have to be VERY careful. Faraday pouch 100% of the time it’s near your house, lots of extreme steps like so. If the new FCC rules go info effect tho, it’ll be almost impossible b/c the carrier just won’t give you service unless you gave a photo ID.