On the seat? Most porters I know of on YouTube radius to the 60 deg on both and smooth the chamber to the 30 deg.
I’m thinking the 5 angle is the machinist way to make a better transition into and out of the valve seat when not porting with a die grinder.
If you have faith in your porter and he has a good rep, trust him that he did what was best. Most folks of modest means can’t afford a set of heads ported by Darren Morgan. Is it worth it to you for that 5-10 hp more? If you have the cabbage, get to Darren.
I like champagne,but I’m still drinking beer.
Even though the valve and seat is the greatest point of restriction in the head port, there are other things to consider like efficiency and port energy. A ported intake and the right sized carburetor properly massaged greatly enhances your combination.