I don't think you are wrong; it's just that a lot of people here on this thread are current or former Googlers. Compared to them, you don't know Piper so your argument is at a disadvantage.

My perspective is simple: inventing its own source control system at Google is absolutely worthwhile and the ROI is highly positive. The tradeoff is worthwhile. You might say that before Piper existed it might be a gamble whether it would be worth it. But in hindsight, absolutely 100% yes it's worthwhile. It does not need to be argued, for anyone who has used it.

The only thing that is really subject to debate is whether Google's engineering leads had the foresight of what Piper would accomplish or whether they simply wanted to build something custom due to NIH and it only fortuitously turned out to be good. That's a question no one here can answer.