To expect CRT/Williams Tube memory is a slightly bizarre assumption, it's a technology that was only very briefly used (developed in 1947 and used only in machines in the early 1950s, all but disappearing by 1956). It's also pretty much unheard of now.

While magnetic core memory was dominant from 1955 until around 1976, when silicon went mainstream. Machines with MCM were in general use for a long time after that too.

It's possible the interviewer confused the widespread use of CRT in pre-flat screen monitors. (Shrug, maybe CRT was very briefly mentioned? who knows?!)

Williams Tube memory is pretty interesting BTW. Worth taking a look at Selectron memory too. You know, for fun.

This is the one thing the article got wrong about the talk. The 7074 replaced magnetic drums with core memory. It's an easy mistake to make since the 700 series used vacuum tube logic and the 7070 replaced those with transistors. The 7074 came about two years after that.

I think the implication wasn't that they were interchangeable, but that the machine they were expecting to see used CRTs, and instead, they found it using MCM.