All signs point to my harp actually having less tension on it.  Whew.

From http://liutaiomottola.com/formulae/tension.htm
A few things should be apparent from the formula:
1. Everything else being the same, pitch increases as tension increases;
2. Everything else being the same, tension increases as scale length increases;
3. Everything else being the same, tension increases as unit weight increases, thus a heavier gage string will be under greater tension as a lighter one of the same length tuned to the same note;

This is not tension as in how it feels to play - that is referred to as compliance of the string, and that is the subjective "these strings feel tight and are more difficult to play" feeling the musician gets.