In this instance though there are no reasons.
Men never usually have trouble making comments about the time of the month should you dare be annoyed at them for anything 
Its certainly unfair in this instance to go against what the dd has asked and I'm surprised that a post about female biology can become all about a man.
The pp o was responding to was talking about flagging it up but spoke in a way where the onus was on the girl to tell the dad in the first place or how could he possibly know.
They should not need telling.
Men know all about biology when they wanna look at porn on the internet.
They know all about periods when they can use then to make derogatory comments.
They know how young puberty can kick in when it comes to labelling inappropriate boys behaviour as " typical boy" stuff
I dont buy that they cant figure this out. Plenty of male primary teachers will have a stash of stuff should a girl need it at school. Those kids arent even theres.
I think.its sad that periods are seen as something that men either need a heads up about incase they accidently see something. Or something men cant possibly be expected to cater for on their weekends with the daughters and need to be told/reminded to provide basics.