Here's an algebraic example to keep things theoretical. If the easy to delete version proposed by the article is:
f(x) = 6x^2 - 5x + 1
The
prospective extensible version is:
g(x,a,b) = ax + b
f(x,q()) = q(x,3,-1) q(x,2,-1)
f(x,g)
It's the generalization for factorable polynomials. It's clearly harder to read than the easy to delete version. It's more complex to write, and so on.
However, it's algebraically orthogonal. It has advantages in some cases, for instance if you later add code for a 6th-order polynomial and need to use its zeroes for something else.
We know that it could be better in some cases. Is it a good bet to predict that it will be better overall? The problem domain can fracture across a thousand orthogonal "creases" like this one. The relevant skill is in making the right bets.
Here's an example that's not orthogonal. Let's say we think the 6 coefficient might be more likely to change in the future:
g(x,a) = ax^2 - 5x - 1
f(x,q()) = q(x,6)
f(x,g)
This version is most likely just adding complexity. A single function is almost always a better bet.