Quite a lot of hubris in thinking they are just going to solve this as if no one has been working on it. Who knows, maybe they have, but color me skeptical.
Are there any well used GC that aren't tricolor?
Server GC, for example, typically tends to be less concurrent to improve throughput. Client GC is more responsive, but also sacrifices throughput. Since Go is positioned for server work, it is very interesting that they are choose what is typically seen as client-side priorities.
Also, I think its really important that pause times be as short as possible on the server as well. If they aren't, you'd probably see an unhealthy spike in 90+ percentile responses.
Not kidding, though, the latency hit from stop the world only gets worse scaling from 32 cores to 64. May as well call it "batch" GC. On the other hand, concurrent GC will keep the same latency but hopefully double throughput on such a machine.
They say[1]: Limiting GC pause times is, in general, more important than maximizing throughput. Switching to a low-pause collector such as G1 should provide a better overall experience, for most users, than a throughput-oriented collector