Since they didn't mention a computer line but rather a CPU, I assume they used "base M1" to mean the CPU called "M1" as opposed to the "M1 Pro" or "M1 Max" or "M1 Ultra". I don't think they were referring to "base M1 MacBook Pro" or "base M1 MacBook Air" or "base M1 Mac Mini".
And they're right, the "base M1" (as in not the Pro, Max or Ultra) is a very capable chip.
And they're right, the "base M1" (as in not the Pro, Max or Ultra) is a very capable chip.