Advantageous Root Growth created a Hour Glass shape .....what is the correct gardening term for this

Tree planted to deep from probably a 4" liner

On the received plant I got, I started pulling the soil to check for any needed root correction. Advantagious roots 2" above the bottom of the flare ......roots growing and it was fatter/thicker/bulbous than the leader below it.

With the soil now at the correct depth, it basically looks like a hourglass figure in the trunk.

What is the correct gardening terminology for this. Misplaced-displaced energy ?