You probably won't like this answer - I have no idea.
You can't blame the etchant!
Did YOU do the proper steps to arrive at a result that WILL SHOW?
If there's nothing there for the etchant to expose, you can't blame the etchant.
If you've done your job right, and properly created a hamon or quench line, then only a few seconds in the etchant will show it.
This will show how well you did your job.
Proper steel, (meaning one that WILL show a line like 1084/1095),correct post-forging steps for grain refinement, accurate temp control during hardening with the correct quenchant, and good finishing techniques of the steel surface, and cleanliness!
If you haven't got all those ducks in a row to actually create the quench line or hamon, there's no etchant in the world that will "etch" what isn't there.