Al, hopeful to put this disagreement to conclusion: "the engineer has to understand the implications of what is proposed as an alternative to the code requirements."
Obviously, this goes without saying. Whether I'm working on a structural job, piping job or vessel job, I / we have to consider the mechanics of the materials with respect to the loads / forces / connections / joints. I'm most certainly not qualified to make all of those determinations by myself but have to involve other discipline engineers (Civil, Structural, Mechanical, Process, etc). There's are a myriad of considerations. (Yes, believe it or not, some of them even consider quality issues and ASSUMED defect factors).
Those "other" discipline engineers make certain calls which are within their areas of expertise. I look more specific at things like tensiles and if required, hardness, macros, impacts, corrosion tests, etc. Bend testing, while required by both ASME IX and D1.1 seem a bit redundant to me. Omer Blodgett wonderfully described bend testing as "a poor mans tensile test." It is what it is and until such time that the Committee's agree to remove it in favour of tensiles, it shall remain and be done.
To be sure, volumetric quality could play a crucial role in the pass / fail of a PQR, but these issues would also be evident when mechanical tests are performed. They are not inherent to material properties if a good selection is used but instead are performance related. If the "engineer" selected an alloy that didn't match and God forbid, transverse cracking occurred as a result then that engineer's judgment is what should be questioned, materials don't lie and are inherently stupid by themselves! :) That's why we focus more on the mechanical properties during qualification but rely more heavily on NDE in construction / fabrication.
If the mechanicals prove themselves adequate for intent, then the major concern becomes the ability of the welder.
It's clear from this discussion you view issues from a quality perspective while many of us view them from an engineering perspective. Your thoughts are welcome and the vast majority of your points are worthy when considering quality perspective, they're just on a different thought process than those of the engineer. It is the engineer who take responsibility, quality simply follows the direction provided by the engineer. Rest at ease my friend, there may be plenty of idiots out there, but there's also a few of us that know our stuff! :)