Sorry, can’t answer the PHR question, but can vouch for good quality alloy nipples, I built some gravel/CX wheels with Sapim alloy nipples and Sapim spoke washers, borrowed a spoke tension meter so have the spokes tightened to the max tension the rim will allow (1300Nm if I remember correctly).
Only concession I made to alloy nipples was using a bit of copper anti-seize, because why not.
Wheels are just over a year old now, have taken a bit of a beating and a lot of muddy miles, no seizing, no cracked nipples, still running perfectly true (the only reason I know the nipples haven’t seized is because I re-dished the rear wheel slightly).
I think a lot of the horror stories about alloy nipples are based on cheap nipples or uncoated bare alloy nipples or something.