Oops, I wasn't clear. I'd meant that, if I recall correctly, the HotSpot team initially experimented with combining the 'client' and 'server' JITs for tiered compilation, but decided it was a lot of complexity for little gain, and didn't commit.

Only a couple years later did they re-attempt it and stick with it.

I could be mistaken here, and I wasn't able to find anything online to support me.