The way it breaks is identical to how it breaks for me as well.Uhh, Thanks!
I had six hours on those strings, and you are right that it is interesting it will break at the grommet but not at a notch. I had just hit two screaming groundstrokes right before that.
Looking at that first picture I posted, the two strings closer to the middle from the break pulled back, and its interesting to me that even on the fourth cross down, I'm hitting enough balls up that high on the stringbed to cause denting/notching. I know that with this racquet, serving with a higher contact point is beneficial because there's still excellent pop up high and I get the advantage of a bit more RHS further from my hand.
I'm pretty sure your analysis is right - it's just whatever they did to create the crispness and tension maintenance to the string. Like you, I'll also continue to use this string, at least during the winter. I haven't found any other string that gives me the confidence to swing away, the comfort to do when when it's cold, and the long lasting playability.
It also happens after a few hours are already on the string bed.
Quite a few people are saying the 17 gauge feels thinner than other 17 gauges. I did measure with a micrometer and it was 1.25mm. Maybe someone wants to confirm?
I saw on an old review of SPPP mentioned premature breakage as well: "However, it happens to me at least 5 times that there is premature breakage right at the last grommet near throat for open string pattern racquets (such as ProKennex 5G, Dunlop AG100, MG Prestige Pro)"