I don't think you need 3 knives, although in my BOB I have 2.Are three knives the minimum?
While setting up a bug out bag I got to thinking about what kind of cutting tools or knives would I need. I decided that one knife was not enough I could get by with two but three knives would cover about anything I could possibly need a knife to do.
The three types of knives that I came up with were...
A heavy full tang fix blade knife, something such as a BK 2 or ESEE 5. For heavy chores like chopping batonning.
A medium weight fixed blade knife such as a Mora or Condor bushlore. For finer cutting and fashioning gear dressing game etc.
A pocket knife. Which is also an EDC item and would be useful for fine or light cutting chores.
I think that covers most uses for a knife one might encounter while bugging out. I do believe I could add more but think three is a nice number...and of course I'd include a stone to keep them sharp.
The first is a fixed blade knife, the 2nd is my backup on my multi-tool
It is better to have a way to sharpen the 2 knives I have than a third that will take up space and weight.
The other thing to consider is salvaging items off the dead corpses you encounter as you bug out, in that case a good particulate mask and some disposable gloves will be golden.