You are simply wrong regarding +ABL investigating to "figure out if the consecrating bishop was new/old rite" - he considered the rite, as is, valid. Period.
+ABL and +Williamson considered Fr. Hesse's NO ordination valid. Old Rite Bishop/NO Ceremony. They considered (I cannot remember his name but Fr. Hesse said it in his talk) new rite Bishop / old ceremony valid. How could this be if all NO consecration/ordinations are invalid as you said?
I have had numerous priests, both SSPX and independent priests say what I've been saying - validity is always initially presumed with the NO ordinations.
The old and new sspx was wrong to presume validity. Even +Tissier wrote a lengthy study in early 2000 where he said such doubts are positive. But they've gone back-n-forth on many different topics. Nothing wrong with this, as we live in crazy times. But I will not accept "revisionist history" that says they've been 100% consistent.
The concern is as Giovanni posted, the translations, the ad libbing and the intention of the ministers, not the validity of the original (new) rites in Latin.
That was +ABL's concern. He doesn't own tradition and never did. Plenty of others disagreed with him (and still do).
The landscape has changed, but the principle has not and can never. Nothing in this world is worth risking committing a sacrilege. The SSPX knew this then and knows this now, even if the whole world insists otherwise, or insists they're wrong.
This "principle" you keep bringing up, doesn't apply. It only applies to legitimate, legal, morally approved rites, which the NO rites are not.
And there's always the case of imminent death when only a NO priest is available, what, is the priest suddenly made valid for the occasion, then afterwards returns to being invalid?
I also don't think you understand the difference between the following. Your example above makes no sense.
a. Negatively doubtful validity
b. Positively doubtful validity
c. Positively (or 100% certain) invalid