He didn't say ocellaris don't have black around the white, he said percs don't. He is still wrong, although I have seen some percs without a black outline, especially if they are young.
I didn't get that one - it's even worse.
But I saw that false statement about ocellaris in some books or websites and it's just utter nonsense. Both species, ocellaris and percula, can have quite heavy black borders around the white bars when living in carpet anemones.
On the other hand, the black line will virtually disappear in both, ocellaris and percula, when living in a H magnifica.
The part that has not yet been properly researched is if certain strains of each species prefer either anemone. There is some research that points towards this - that the larva get imprinted with the chemical signature of their parents host anemone while still in the egg, and later look for this signature to settle down.
There is certainly less black in ocellaris that come from the southwestern region of their range (Indonesia, Singapore, Malaysia) while the ones coming from the Philippines often have more black.
The above fish looks very ocellaris to me me. I can't see anything that would make me think percula.
I kind of agree. What makes me think twice about calling it an ocellaris for sure is the relatively shallow hard section of the dorsal fin. In percula it is usually lower than the soft part while in ocellaris it is the other way around.