Make it clear that max_live_bytes is updated after a major GC whereas
live_bytes is updated after all GCs (including minor collections) and
considers data in uncollected generations as live.
Might also be good to say something like "if the previous GC was a major GC, then this is an accurate measure of the current live data."
You can track actual live data by using this value after a major GC, and ignoring it at other times. On the other hand, this figure is a useful measure of how large the old generation has grown, so that we can see how large it gets before we collect it. So while it seems like a slightly odd statistic, in practice I've found it quite useful.