Maintaining a stateful websocket connection on the server side isn't cost-free, and that connection would be idle nearly 100% of the time. The bandwidth consumed via Google's polling solution might well be cheaper than open socket file descriptors of a websockets solution.
You make it sound like it would have taken months of investment to just use one of the many available better options - at worst, it might have taken a week for somebody to learn web sockets if they actually didn’t have anybody who knew it (and even then, that’s a slow learner). We should be delivering the most efficient options and always weighing the alternatives - we’re professionals, maybe some day we’ll actually start behaving that way. From the top-level responses to this article, today is not that day.
I really like the polling approach used here. It’s simple, easy to reason about, and loosely coupled. It will be reliable and resilient.
Saying it might have taken a week to learn websockets completely misses the point. I’ve built large architectures on persistent connections and deeply regretted it.