I think the rule is terrible, and the reasoning given for its creation is nice to listen to, but reaches a flawed conclusion.
Tangent about rules: the worst thing (in my opinion) about rules that have to be followed is the effect they have when they steer you to the edge of a cliff, and then tell you that you have to jump off. Absolutely painful to endure. This software reuse rule isn't that bad, but with all the bad rules being enforced in my daily life, this tangent was a must-take for me.
If you have old useful code that you will have to rewrite from scratch, then please be careful! Its really easy to make a mistake..