Exactly! My soil is actually so high in phosphorus that I could cause problems if I add more at planting time. I posted my soil test a few years ago here, you can see it’s in the “very high” range:
I sometimes mix a little compost with my backfill because my soil is so low in organic matter, and because I want to make sure I have enough backfill for the tree to be slightly above grade, but I don’t add any other amendments, I mostly just top dress with compost and mulch.
Same! That’s why I started doing it. But just with water, nothing added to the water. I don’t usually do the full 12-24 hours, I just throw them in buckets of water when I unbox them and usually plant them later that same day, occasionally the next day.