I've been testing it for a bit and I really can't see any difference, at least with the stances equipped. Either the tip of the whip is actually extending with the Reach mod so that it still visibly hits enemies, or Reach doesn't work at all. But I think we'd notice since 60% is actually a big deal.
Burning Wasp feels like you're hitting a good 2 meters away on the first 2 hits in the combo (the third hit is a lunging attack that actually has a short range from the whip itself). An additional 60% of that would be something like a total of 3.2 meters away, which is a huge AoE that people can't really mistake.
Also note that Reach really has that effect on long range melee weapons. With the Orthos it's very visible like I said in the first post. Even with shorter weapons like a Pangolin Sword, you still see that you don't actually need to have the blade touch enemies sometimes in order to score a hit. Obviously since it works by adding a percentage, the longer the original range, the bigger and more obvious the effect is supposed to be.