Earlier quoted context omitted.
But from a company's perspective, isn't that 23% the only number that matters? The point of the study (and I have some issues with it too) is that the 23% could be 30% if you dealt with the toxic employee, or at the very least 23% is still doable without them, even though it seems like it isn't because they're better than average.
I get the concept of what you're saying with, "the 23% could be 30% if you dealt with the toxic employee", but I think that unfortunately is not true in a lot of cases. There are a lot of really talented, hard-working people who are also toxic leaders (some maybe not fully intentionally), and the challenge of dealing with them in an organization is that, as you point out, measurable performance is often all that matt…
It's never worth promoting a potentially toxic manager into a managerial role, even if they're great in their current role. If you do, the whole team suffers. If you don't and they leave because you didn't promote them, they weren't going to let you keep them as an IC anyway. Best case is you reform them, but do that before and not after you promote them.
I've seen this pattern more than I'd like.