I don’t have high hopes for a quick bearing P.18. Fruiting quicker than Antonovka sets a pretty low bar. I planted a Chestnut crab on P.18 in 2019, so that may give me an idea on what to expect. I’ve planted 7 others since then (5 varieties).
Interestingly, a Goldrush on P.18 that I planted in 2020 produced blossoms in 2021. I let one apple grow to maturity and it was still hanging as of 10/28. Another Goldrush I planted in 2018 on B.118 began producing nice crops the following year, 2019, and has been ever since. I don’t recall Goldrush for being noted for precociousness, but my limited experience indicates it is. I kinda veered off-topic, but hopefully the Bonkers I/we’ve ordered on P.18 rootstock will produce fruit in our lifetimes.