Big kudos to everyone working on it (most of which are Google engineers, some very senior) but I can't help wonder what other issues might be lurking if that one went unnoticed for so long.
The thing that went unnoticed with that issue is that grpc-go didn't have an option to manually increase the window size. Both the Java and C implementations had the option much earlier; I see a commit adding it in Java in March 2015.
At least by August 2015 I was working on automatic window size tuning, which I've not seen in another HTTP/2 implementation to date. July 2016 it was implemented in Java, but remains disabled due to interoperability concerns that we need to spend time addressing. C now implements something similar and it may be enabled in 1.3.
For flow control to work promptly the window size should be only as large as necessary, so there is cause for keeping it small. Since the lower value is appropriate for many networks, it isn't completely outrageous.
I think the biggest failure on gRPC's part here is not having a notice in a widely-read part of documentation informing users to be aware of the limitation. That's easier said than done, but that doesn't negate its importance.
Big kudos to everyone working on it (most of which are Google engineers, some very senior) but I can't help wonder what other issues might be lurking if that one went unnoticed for so long.