FWIW, the base images they're talking about do not contain an entire OS. In fact, they're lacking a colossal amount of the most basic stuff that qualifies as 'an entire OS'. In many cases, your base images are 'a program to install more stuff if you need it', a shell, and coreutils.

For debugging image it's sometimes nice to be able to actually do stuff in the container, but for production image I'd agree.