I don't know if I've ever seen a java application where performance is so maxed out that this was needed. Not to say that they don't exist, just that it seems like an unnecessarily complex knob to turn.
Just last week, I was helping with some performance tuning on an application that needs to match some set of criteria against tens of thousands of rules, and needs to do so in around 30ms under fairly constant load. Hitting our latency/throughput targets required a lot of tuning, especially around GC. Among other things, it was important to make sure most/all of a request could be handled in the TLAB.
I could definitely see something like this giving us a few more milliseconds per request, and I'm definitely going to try it out in a next round of performance work - always nice to have a bit of head room.