When a large force is applied unintentionally to a finger we have the problem.
With a dull knife you need to apply a larger force than with a sharp knife.
[The video illustrates this with breaking the skin of the tomato.]
For a normal cut this is not a problem.
But - if the knife slips and a large force is applied at the same time - then you will get a large cut.
If the knife slips and a small force is applied, you will get a smaller cut.
If the probability of slipping is the same for sharp and dull knifes,
then due to the forces applied, the cuts you get with a sharp knife are less dangerous.
But - if the knife slips and a large force is applied at the same time - then you will get a large cut.
If the knife slips and a small force is applied, you will get a smaller cut.
If the probability of slipping is the same for sharp and dull knifes, then due to the forces applied, the cuts you get with a sharp knife are less dangerous.