complexity theory – Why the measuring of characters replaced with the same character in the tape of a Turing machine doesn’t isn’t a valid measure by Blum’s axioms?


In Computational Complexity of Papademetriou, there is an exercise about Blum’s axioms where it asks to prove that several measures for the complexity of a Turing machine satisfy them.
The last one is about the number of times a character is replaced by itself in a Turing machine, where it is asked to prove that this doesn’t satisfy Blums axioms.
Why doesn’t it satisfy Blums axioms?