Nissan Altima: 2003 Altima Engine Self Destructs

Hello, I'm new to this forum and I'm posting this question on behalf of my
brother-in-law. He owns a 2003 Altima with 92,000 miles on it. He owned the
car for 15 months (bought it for his son) and resently had it serviced due to
some codes being thrown regarding the oxygen sensors. He had to bring the car
in for servicing four times for the same problem, O2 sensors kept going bad.
This was over the last 6 months. He was not bringing the car to the
dealership but to a qualified Nissan mechanic. Then, he was getting a check
oil light as well as check engine light. His mechanic said only the sensors
were going bad but with oil being burned big time, he did the right thing and
brought the car to the local dealership.
It was determined by the dealership that his engine was pretty much
destroyed, not due to his negligence but due to a bad cadalatic converter.
Apparently, the converter disintegrated and somehow the engine sucked back
the particals from the failed converter and compromised all of the seals in
the engine. That would explain the sudden loss of oil and performance.
My questions are, has anyone ever heard of this happening before? Was
there ever a recall of this part? Any technical service bullitens? Given the
age of the converter, I suspect a bad part. He said that the dealership
tracked the vechicals history and the converter had been replaced once before.
Is it possible they installed another faulty converter??
When he purchased the car thru the dealership he also purchased an
extended warrenty for 1000$ for an additional 3 year or 36,000 miles. He was
shell shocked when he learned that cadalatic converters are not covered under
the extended warrenty. Needless to say he is royally P.O.ed at his mechanic
for not diagonosing this problem earlier (4 trips to his mechanic).
I guess the lesson learned is bring your car to the dealership for servicing
and not some other mechanic. Strange thing is that his mechanic claimed to
have the same diagnostic computer as the dealership and never had an
indication of a bad converter (so he say's).
Now, he needs to shell out 4500$ for a new motor!!! (installed price)

Sorry for the long winded post but I felt the need to explain the history
behind this.
Comments are appreciated!
Thanks

I was recently at a dinner and there was a mechanic that was in charge
of the Nissian dept. for a large dealership. He said that there was a
new engine manufacturing process that had hardened the pistons and
cylinder walls on th 2003 4 cylinder Nissians that was preventing the
engines from breaking in properly. This was resulting in excessive oil
consumption, a degeneration of the catalytic converter, and ultimate
destruction of the engine. Can't vouch for the conversation, but I
looked up your posting when I got home. Looks like the problem he
described. Does not make me feel good as we bought a 2003 Altima used
and so far have liked it. Sounds like I should dump it.