Ook wrote:
untreated wood into concrete ~10 to 20 years depending on location &
environment

Around here - rain all the time - I keep hearing 10 years from locals. I'm
planning to be here for longer then that, don't want to have to dig them out
and replace them in 10 years.

A deeper socket would be better but they must have done some tests?????

Maybe, maybe not. It's possible they did some tests and this is the next
best thing since sliced bread. It's also possible they did some preliminary
tests and just dumped the things on the market. So, take a 100 foot run of
fence. Imagine the posts being held by a 4-5 inch tall pinch bracket.
Imagine a 20mph wind blowing. I can just see the entire fence blowing over.

I really like this idea, so I'm researching it to see if it's viable.

buy one or two & do some experiements with them

Yeah, I will probalby do this. I'm hoping someone here has actually used the
things so I don't waste $20-$30 in case they are not useable for a 6 foot
tall fence.

I've seen them but never used them. I was under the impression they
where sold for "repair" not new construction.

I would be concerned about the long term strength & stiffness of the
wood / bracket connection.

I suggest you visit http://www.fpl.fs.fed.us/

They have a great deal of information about wood & the design of wooden
structures.

I assume you're interested in the best perfroming, longest lasting
wooden fence at a reasonable cost.

IMO perhaps these brackets are not the best use of resources from the
point of view of post longevity & fence strength / stiffness I'm not a
huge fan of wood posts into the earth but some effort put into post
hole prep might be more cost effective than these brackets.

If you're designing a fence for longevity you need to take a look at
the entire system. As soon as any part of the fence starts to fail,
you go into repair / maint mode.

Things to consider

Treated posts ,
stainless fasteners,

post hole prepped for drainage

continuous (ie spliced double) top rail will give you some moment /
load transfer from section to section so the whole thing works together

some sort of bottom horizontal board worked into the desgin so rot /
termites only effect on board per section rather than 16

May solution to a 75 year old wood frame / stucco fence (no wood left
at this point stucco only) on a concrete footing .........

A CMU wall

cheers
Bob