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You are incorrect sir... both accounts. The first Hypoid ring and pinion was invented by a trio of companies and patented in 1935. Ford motor company, Shell oil and The Gleason Works.

As for the 9" being stronger due to its pinion off set, one of the contributors to its weakness is its pinion offset. The fact that the crown is engaged by the pinion almost under the crown center line creates crown deflection due to the vector forces alignment with regard to the ears of the carrier bearing journals (limited to no lateral support). Meaning the vector forces are trying to push the crown and pinion away from each other deflecting the carrier bearing journals (one reason for draw thru cap bolts)and ahead of the rear pinion bearing. The reason for this potential deflection is the further the force generation from the bulk of the casting the greater the deflection will be (BTW the 8 3/4 has similar issues). Un-like the 12 bolt and Dana where the force is generated directly between the caps and over the rear pinion bearing. This brings me to the fact that a 9" needs a crown support to keep the crown from folding over in high HP apps as well, another feature (this time from ford)is the rear pinion bearing to bolster the 9" strength for everyday use, with out it. the pinion head simply pops off.

You are correct that more tooth engagement typically relates to a stronger gear set due to less tooth deformation but the gear on the 9" does not suffer from tooth deformation it suffers from system deformation.

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Pardon my mistake ...the Hypoid gear was introduced by the Gleason works in 1925 not 1935...BTW The very first Hypoid pinion has been in my hot little hands (about 10 yrs ago)when I worked for Gleasons.

I believe people confuse a Hypoid for a Spirial Bevel