Many would interpret this to be true: that if one is genuine to oneself, they can never then be deceptive to their lover.
Though it may not be inaccurate to some extent, it subliminally tells the readers, women in particular, that the prime reason to be true to oneself is to satisfy a man's superego.
To maintain a man's dignity and pride, what more can they have than a woman's loyalty and honesty to do so?
Because Hamlet is the main character and a male, it would be rather unorthodox for a female character of non-stereotypical traits to share the spotlight or even as any significant character.
The women used in this play are portrayed as mere accessories, only working to worsen the conditions of the main male character's situation; therefore, causing the readers to sympathize or agree with him.