Have you tried loosening the pivot screw/ unscrew the threaded torx screw a fraction of a turn ?
I have the HO I and the HO III. Neither one was hard to open even out of the box. Mine are bare CTS-XHP. Maybe the black coating is dragging or gobbed up.
If you take the knife apart it may become obvious where to touch a grinder to totally remedy this problem. On my HO I (the largest knife) I had to really press the unlock lever far into the scales of the handle to get it to unlock. Not a problem the first couple times but after frequent opening and closing fatigue and almost what I would call bruising of my fingers would set in (and I have callused hands from all day mechanic work) and it would get to be where I had to concentrate too much on closing the knife and or use different fingers to close it.
Once I ground an angle across that little corner it is easy to close over and over and does not compromise the strength of the lock.
surfaces that slide when opening the knife
I found mine to be better polished than I expected. I had planed on taking a diamond file and then carborundum paper to mine but all I did was admire those areas and put it back together. I am not convince that even if these were just stamped and not ground smoother that it would make the knife much harder to open I just was going to do it out of habit and the hope of making the knife extra smooth etc.
Have you found areas that were rough and smoothing them actually made it easier to open?
Hard to sharpen large knife with CTS-XHP
No problem. I recently ran the edge into a metal tool while cutting with the knife and dinged up the edge . . . ha, ha, but not as much as the knife dinged up the tool it ran into . . .
I used Shapton stones on the Edge Pro starting at 500 and the edge came right up to hair whittling in no time. The only questionable anomaly was that the bevels on each side of the edge looked even from the maker but when in the jig I had to use radically different settings on the jig to hit the edge. I haven't measured the faces of the blade but suspect they are not evenly centered on the back of the blade. I don't know how to explain that any better. The back of the blade and point are centered in the handle though. I find this to be true on most factory ground edges. I wish they could automate the sharpening like box knife blades are then I could, in theory, just chuck the knife into the jig and sharpen it brainlessly.