Wow. They're right.

I checked a number of NZ urology sites & they all agree.

Above the age of 75 we do not recommend routine screening as the risks of investigation and treatment outweigh the potential benefits.

Being tested for prostate cancer is your choice. Your decision depends on:
whether you have a family history of prostate cancer in your father or brother (this doubles your risk of prostate cancer).
your age and life expectancy – if you're over 75 years of age, or expect your lifetime to be less than 10 years, you shouldn't be tested for prostate cancer as the harm is higher than the benefit.

There is no strong evidence to suggest that testing men over the age of 70 years reduces
mortality from prostate cancer in this age group. Generally men aged over 70 years, who have a normal-feeling prostate on digital rectal examination (DRE) and who have had ‘normal’ PSA tests in the past, should be advised they are not likely to benefit from any further PSA testing.

Maybe a subsequent biopsy is too invasive a procedure at that age, or recovery is more painful/difficult?
Must be the whole 'do no harm' thing.