Multiple publications (including this one) came to the logical conclusion that Al Carey, who will be adding Greco’s responsibilities to his current role as head of North American Beverages, was being positioned as a successor to Nooyi.

But that’s not what’s happening at all. Instead, Greco’s departure highlights two ongoing issues at the $63 billion-in-revenues PepsiCo: the ongoing loss of top executive talent and, perhaps related, Nooyi’s reluctance to announce any official succession plan, something that most longtime CEOs emphasize is one of the most important parts of the job.

For starters, Al Carey is not likely to be a future PepsiCo CEO, though he is admired and respected within the company. The most obvious reason is that he is older than Nooyi: 64 to her 60. His promotion, then, is the equivalent of putting an old hand back in—he previously ran the snacks business before moving to beverages—rather than elevating a potential successor.

Yesterday’s announcement actually occurred because Greco, 57, decided to depart. It was not part of any organized plan on behalf of the board of directors. Greco, the company said in a statement, is “leaving PepsiCo to pursue his long-standing career goal of being CEO of a company outside our industry.” (He has not yet announced which company.) This is only the most recent of several top executive defections, which include Brian Cornell, now CEO of Target, Debra Crew, now at R.J. Reynolds Tobacco, and, about nine months ago, the rising star Enderson Guimaraes. PepsiCo’s longtime response to this is that it is perceived as a training ground for top executives, and it is true that many of these people have gone on to the corner office.

The other reason that PepsiCo’s move is not about succession is that Nooyi, who has done an admirable job of keeping PepsiCo going in a time of dramatic change, seems to be allergic to the topic altogether. I have written about this issue before, and what strikes me every time I bring it up is the immediate defensiveness with which the company reacts to any suggestion that Nooyi might ever consider turning over the reins. To wit: When I asked what the succession plans were, a spokesperson was quick to send me a statement saying PepsiCo’s directors have full confidence in her leadership: “The Board is strongly committed to supporting and retaining Ms. Nooyi for the continuation of PepsiCo’s transformative journey in the upcoming years.”

But I wasn’t suggesting that the board didn’t have confidence. I was wondering why there was no true No. 2 in place who is being trained by Nooyi for when she is in fact ready to leave. (Or in case something happens to her: Remember how the United Continental CEO resigned, only to have his successor need a heart transplant? Or the two McDonald’s CEOs who died within a decade?) To that question, the company trotted out an old saw: “Our Board has robust succession planning processes and we have a deep bench of well-rounded, seasoned leaders running our businesses.”

Needless to say, the statement offered no specifics.