I was more trying to explain the intuition of why single nucleotide mutations (resulting in non-viability or undesired effects) are probably more likely in a strand of DNA with regions removed versus a strand of DNA left as-is.

Basically, trying to give an example of the grandparent's point. (i.e. fewer nucleotides to be flipped -> more likely that an important one will be). I agree that it was a poorly executed analogy. The metaphor I was trying to make is that on the 'vast field' a random single point mutation is probably going to land on an individually unimportant nucleotide, and in the 'narrow beach' (the smaller strand/higher geninfo density) an individually important nucleotide is more likely to be hit. I'm still probably not articulating my point well, sorry.

But I think your analogy is better for a subtly different point; describing how DNA replication works in a system, where stands can be selected out, errors corrected, and genetic information can be preserved at a systemic level.