I personally don't believe that Winger understood anything that wasn't well understood by both Apple and IBM at the time.
I would say that this passage is pointing out the confusion that Apple's approach to "computing in the workplace" bore little resemblance to IBM's well-established approach to "computing in the workplace." The commentary is attempting to dissect what is happening in two distinct markets by falsely viewing them as a single market.
You first have to remember that computing for business and scientific work was nothing new in 1980. The computing business had been around for a couple of decades already, and IBM had grown to own the largest share of that established market. In contrast, Apple was a startup in the new business of microcomputers for personal use. This was not the same market as IBM. You could certainly argue that microcomputers were already showing the promise that they'd revolutionize legacy computing by 1980, but that was much more a prognostication than an accepted fact. The typical corporate IT purchasing manager certainly had no reason to risk their job over speculation about the future of micros.
So, when IBM finally entered the microcomputer for personal use business to compete with Apple, they weren't entering it as a startup. They already had legions of loyal customers who owned IBM products for business and scientific computing. The task for IBM was to simply guide those existing customers toward microcomputer adoption. Apple had no such opportunity to market in this way because they had no such existing customer base to whom they could direct this marketing. Had Apple made an attempt to do that earlier, they would have met with much resistance from the "typical" computing user thinking something along the lines of "If this is the future of computing, then why isn't IBM selling it to me"?
Now, it is not as if Apple was blind to the opportunities for micros in business and scientific computing, just as IBM was obviously not blind to it. They were already maturing their product line to address these exact markets with the Apple /// and the Lisa. These were to be higher end products that could be marketed to traditional computing users on their capabilities. They weren't just a low-end microprocessor in a personal package; but rather sophisticated systems with state-of-the-art OS software geared toward workplace uses and not toward playing "Karateka".
Apple had every intention of leading the revolution in corporate and scientific computing and "stealing" IBM's legacy customers away from them. It didn't work out that way because IBM severely upset their Apple cart by executing rather brilliantly with a personal computer bearing their own trusted and established brand.