This is really cool! The chart on that page makes it look like Leela Zero is already much much better than AlphaZero (~7400 Elo vs ~5200 Elo). I suspect I'm misinterpreting something though, could you clarify?
Leela Zero's ELO graph assumes that 0 ELO is completely random play, as a simple reference point.
On the other hand Alphago uses the more common ELO scale where 0 is roughly equivalent to a beginner who knows the rules, so you can't directly compare the two.