...and also my 10W-30 VOA linked above has 900 ppm of P and 1000 ppm of Zn......you've got about 100 ppm more of P and about 200 ppm more of Zn.
Blend and sample deviations could explain some of that, but to me it looks like the 15W-40 Shell Rotella T CJ-4 has a hardier add pack.
I wonder though, mine was for sure rated API SM, was your 15W-40? Maybe their both CJ-4 but yours is SL while mine is SM??? That's the only thing I can think of...
Chuck