The Shun deba does indeed have a bevel on both the front and back. In other words the factory grinds the deba incorrectly. They also do this on their usuba (called a nakiri I believe) and Yanagi. So if you lay it flat on the back of the knife, you won't touch the edge of the edge on the back. Also these solid vg10 knives are a major PITA to fix the factory grind. For some odd reason, the abrasion resistance of this knife is really offscale hard to grind.
Why do they do this? Well VG10 is not well known for handling extremely acute angles, so that's a partial explanation. They also are IMO pandering to a western oriented market with this knife. Or to put it less kindly, they screwed up the grind.
I would not recommend continuing to resharpen it along the factory grinds on the front and back.
Instead, I would take down the front bevel as much as you can stand doing. Ideally taking it down to where the 'microbevel' has been erased. This is a lot of work. A LOT of work. A hell of a LOT of work. Once this has been done, you will have also indirectly removed a lot of the bevel on the back of the knife. If you are not quite experienced with this, you will also FU the shinogi line so be careful. Now the odds are excellent that after a few hours of this you will give up in disgust. When you give up with being a purist, here's what you do:
Convert what's left of that front 'microbevel' into a hamaguri grind. Go for a minimal amount of convexity, trying not to round off more of that front bevel then necessary.
Deburr the back using the angle closest to laying it flat on the stone you can get away with. Remember that the greater the angle you use on the back the farther you get from getting to a flat back - ie you are making more work and will need to use up more of the concavity in the back of the blade (urasaki).
At some point you may find that your included angle has become too acute for the steel. If so, just make your front hamaguri grind more obtuse until you are satisfied.
If you are going to do this by hand, cancel your gym membership for a month. If you are doing this with a grinder don't even think about doing it without a platen, variable speed motor and some seriously coarse ceramic belts. Good luck. And don't screw up the shinogi line.
If you are a bit more adventurous, you can change the angle of the entire front bevel to a less acute angle , maintaining the position of the shinogi line, calculating this angle change so that the bevels on the front and back from the factory grinds are eliminated. Thus you will be recreating the entire front bevel and if done precisely you will start removing metal from the edge area until the 'microbevels' are eliminated and see a progression along the front bevel gradually going going up to the shinogi line. Do your triginometry calculations very accurately for this approach or your new bevel won't intersect the shinogi line precisely.
In the end, you will have a much better performing knife than you would maintaining the factory bevels on the front and back of the knife. Maintaining the factory bevels over multiple sharpenings will also make for an interesting exercise in thinning your edge. Interesting in the sense of the Chinese curse of 'May you have a long and INTERESTING life'