McEngr,
Shear lag is an effect, not a strength. It is similar to a Whitmore section when designing gusset plates. The Whitmore section is part of the tension yielding strength of a gusset, but it is not considered the Whitmore yielding strength.
The net section is influenced by the type of connection (bolted vs. welded) and the shear lag effect in table D3.1. I have not heard it referred to as "net section rupture strength", but that is probably synonymous with tension rupture strength. I believe the correct terminology is tension rupture strength because that is how AISC refers to it in the steel manual.