Concerned daughter, biopsies are different from other tests (like PSA in blood, or an image by MRI) where the read-out comes pretty quickly. There is a lot more processing, the samples need to be treated in a way they can be viewed on a microscope slide and the analysis needs an expert pathologist. It all takes time.
It sounds as if the tests so far mean there isn't much doubt about whether cancer is there, but to plan the best approach they need to know how aggressive it is (and where, the cancer can be different in different parts of the prostate). I realise the wait is stressful for you and your father, but at this stage it is about homing in on the best treatment which should be reassuring (somewhat). Although cancer is scary, it doesn't grow so fast that waiting 4 weeks makes a difference.
When I was being diagnosed transperineal biopsy wasn't a thing, I had a transrectal one which carries risk of infection (and wasn't a bundle of fun though I doubt the transperineal one is either). However because the sampling is from the back of the prostate it is easy to take a larger number of separate ones; going transperineally from the bottom of the prostate there is a smaller target which maybe is why they don't take as many samples. (Sorry if that sounds confusing, if you look at a diagram of the prostate you will see that its shape gives it a different profile from those different angles).
I hope that once all the detail is known your father can get the best possible advice, and treatment with a high chance of success.