What does the phrase, “lack pretense of fairness” mean?
It means, it’s not even trying to be fair.
It means it is blatantly unfair, the unfairness showing itself openly with absolutely no effort to hide it - with no effort to use pretense, which is an aspect of diplomacy or tact, to cover it up.
Definition:
An attempt to make something that is not the case appear true.
"his smile is a pretense that masks his hidden anger"
https://dictionary.cambridge.org/dictionary/english/pretence