The size of the top four chambers are significantly smaller in a Short Slot Dark comb™ than a Long Slot (standard) comb. This helps you match your embouchure to the resonance required to control the first semitone blow bend on the ten hole.
If you are struggling to hit that note cleanly in a higher key diatonic harmonica, don't be hard on yourself. It may not be your technique. It may just be physics.
The smaller overall space of the slot decreases the amount of compressible air in the system.
More importantly, the depth of the slot can affect what frequency is reinforced by the channel. The reed dimensions and weight distribution determines the frequency obtained when air flows through the slot and past the reed. But the slot itself can want to behave like a pan flute and the column of air can compress and expand at it's favourite frequency.
On the top end of the harp, it's difficult to compensate for that using your own embouchure alone.
The back wall of Short Slot combs' holes 7, 8, 9 and 10 are closer to the opening than those of a long slot comb. This changes the frequency that is reinforced to one that does not compete with that first semitone blow bend.
You can't change the laws of physics but you can change the slot sizes so that physics works in your favour!
See more about my Dark Combs™ here: Dark Combs