Most all production spec's have a "range" (allowed variation), typically centered around some nominal value. (example: target of 1000ppm phos +/- 5% would be 950 to 1050 ppm).
However, in this case, typical ppm limits are either the top or bottom of acceptable. (example: 1000ppm min phos).
I would say this is just a slightly weak sample; likely due to production mixing variation. Technically it should fail the Ford spec, but I'd not loose sleep over this. The next batch they mixed might have been a bit high? Who knows. There is always variation in production volumes of all products. I do NOT believe a PSD is going to grenade because the lube is down 60ppm of phos from it's rated value.