I think that he's talking about the employee perspective, not the company perspective. Google's tech stack is mostly proprietary, which means you can't take your tech skills with you to a new employer.
...And I haven't found it to be a major problem, being an ex-Googler a little over a year out. Tech skills are easy to pick up on your own. My current startup is based on Node.js, a native Android client, and AWS; the one before it was Django & Heroku. Haven't tried looking for jobs yet - I made enough at Google to not have to worry about that for a while - but I occasionally get in-bound interest from big-name, fast-growing startups. Most clueful hiring managers look for experience with problems, not with solutions, and Google lets you face problems that the rest of the industry won't deal with for a while.
As a Googler I find it to be the most fun and most attractive part of the job. I'm not too worried about learning specific technologies. Learning the core fundamentals of how these technologies work is however critical. But since Google is (still nowadays) pioneering a lot of that, esp. in the distributed world, that's not really a problem either.
My fear would be related to not having things to put on my resume or being able to answer specific questions during interviews, but of course that's not remotely an issue for the specific case of ex-Google employees.
...And I haven't found it to be a major problem, being an ex-Googler a little over a year out. Tech skills are easy to pick up on your own. My current startup is based on Node.js, a native Android client, and AWS; the one before it was Django & Heroku. Haven't tried looking for jobs yet - I made enough at Google to not have to worry about that for a while - but I occasionally get in-bound interest from big-name, fast-growing startups. Most clueful hiring managers look for experience with problems, not with solutions, and Google lets you face problems that the rest of the industry won't deal with for a while.