Richard, you would be wrong in your assumption. It is not poor as general advice, and is the current methodology and thinking, now. Trees will learn to live in their native soils:
https://www.clemson.edu/extension/hgic/videos_posters/posters/tree_planting.pdf
http://articles.chicagotribune.com/2013-03-26/classified/ct-sun-0324-garden-qa-20130326_1_soil-compaction-new-soil-heavy-clay
http://www.ugaurbanag.com/content/better-way-plant-shrubs-and-trees
Bleeding dirt, it can still happen, but hopefully with enough native soil, your tree roots will try to venture out. Truly, you just do not need to do that. You should, instead, be top dressing and allowing the nutrients to percolate down (like Mother Nature does). I don’t think worms really carry organic materials with them, more than ingest them, then poop them out as castings? Maybe we’re saying the same thing 
Now, if you have really heavy clay soil, certainly it is wise to plant your tree (or any plant) on a mound. But as far as amending the hole, it is now considered to not help the tree, and possibly cause root circling. We have a nice thread in this forum about one of our list members who dug their tree up they had planted in a partially amended hole. Sean posted it, and you might want to read through this thread:
Patty S.