how come there is a sharp edge when the second bevel is still visible?
I think that what you've accomplished is to remove the worst parts of the top shoulder of the secondary bevels and so allowed the allowed sharp edge to cut properly. The problem is how to sharpen that edge when it gets blunt. Unless the person who put the secondary bevels on was good, I'm also betting that you have sharpened parts of the edge.
When you cut feather sticks with the grain of the wood, the wood rides up the steep secondary bevels to their shoulder, but then it is your primary bevels which open the cut and pry apart the grain with the edge not even touching anything. So smoothing the top shoulders of bevels has an amazing effect in cutting ability - which here is more of a splitting ability. Unfortunately when used for other cutting tasks, the edge is likely to blunten fast.
It all sounds hugely unlikely, but I am a confirmed believer that I can take a properly finished Mora (bevels) and make it work better by honing the "flat" sides. Essentially I am simply evening out the top shoulders of the huge Scandi bevels, just as you are doing with the top shoulders of the secondary bevels.
Unfortunately, being able to shave feather sticks still won't show if temper has been lost. It's really important to get one knife fixed, and then do some cross grain cutting and scraping. Fixed can mean either going the full route with the original Scandi or putting on a decent secondary bevel with large abrasive surfaces. When the secondary bevels were put on, the edge was probably made irregular - not straight. So a halfway job will only really sharpen the high spots of that edge, and then you might think fast bluntening was due to loss of temper, when it's really due to a poor edge. So you have to get a good edge before making a decision about the shape of the blades.