Frustrating for you and not particularly good patient care but it won’t put him at any increased risk because the hormone treatment will be starving the cancer and preventing it from multiplying. However, when the biopsy is eventually done, it will be important that the lab is aware that he is already on HT as it can affect the biopsy results.
Has he been given the name of a clinical nurse specialist / urology nurse? If so, worth a call to him / her to see whether the biopsy can be brought forward.