Thanks gwegan. I suspected it would come down to a definition. I appreciate the extra that care and spillways and infinity edges require. Here is the language in my warranty.
PB "warrants the pool structure will remain functionally sound for the period of time that the pool is owned by the Buyer or 1 year from completion, whichever is longer. (Coping, decking, colors, plumbing, electrical, filter, heater and other pool accessories and equipment are by definiiton, not part of the pool structure.) The term structurally sound means that the swimming pool retains water. The repair will commence and be completed by PB within a reasonable time after Buyer notifies it of the problem."
Please note that I reasonably assume that "retains water" also means, "doesn't leak" when/where it's not supposed.
There is no mention of rebar, gunite, bond beam or mortar. It only warrants that the pool (and spa) are functionally sound. That is they hold water under normal operation. Nor is there an exclusion of the spa wall as a water tight barrier to the pool. I believe the spa is leaking now or is threatening a leak due to the crack. It is therefore not functionally sound as described under the warranty. It is the result substandard workmanship that used excessively high mortar (> 1 inch) to level the wall without reinforcement to the underlying bond beam and shotcrete.
I also think the spa wall with crack is also a potential hazard to swimmers if part of wall falls into the pool.
Does this shed a new light on the situation?
By the way, would rebuilding the wall with stainless steel reinforcement constitute a change to the structural integrity? The PB has specifically warned that a change to structural integrity (for better or worse) would invalid my lifetime warranty.