"Positional" is like "clinical". It's clean, and easy to categorize and discuss in a so-called intelligent manner. It makes it sound as if it is a reality when in effect it is merely technical. Those who hold heavy to positional truth will make sure you understand that justification means to be declared righteous, but not actually made righteous. They will discuss imputation as if it validates the fact that righteousness is merely a technical counting-to-be-true but not really true.
One of the guys I learned from in the early years of my so-called grace teaching latched onto what he thought was a wonderful distinction. He differentiated between "a" righteousness and "the" righteousness of God. He used a verse in Romans 3 to prove his point that we were given NOT the same infinite, perfect righteousness of God, but a "gift" of righteousness FROM God, which is finite and not perfect in the sense that God is perfect. That ridiculous definition had pretty much sealed the differences between what the two of us saw of Christ's righteousness. But we had been drifting apart for a while.
Positional was simply a theological way (as in Systematic Theology) to hold to the teaching of our new life in Christ without actually believing it. Yuck! I hated that word for years.