
Yes I've noticed!
I have a question: Since your raising up your planting area anyway couldn't one just add a good pile of dirt/compost over the sod and plant into it? Mulch around the plant to hold back new growth while the little guy gets established. This way the ground and organisms are not disturbed, and the old covered sod will decompose and give back it's store of nutrients.....
Kind of a Ruth Stout variation of don't like it, don't disturb just cover and go!