I suppose it is up lift which is trying to be addressed. I have never used the timberlinx connectors before, more suspicion, they would do the task needed.

I was forced to do a similar connection as Jim shows, I bored holes with a drill and cleaned the best I could with chisel. End grain in such a hole is a real bugger.

Tornado alley?

I've done similar to Jim's pic. I used the makita chain mortiser clamped on the end to start the slot, then opened it up with a chainsaw. Not pretty, but got it done.

I'd look into a pipe style connection. If you can change the plate to a 1.25" dia pipe welded to the plate, you can drill a 1.5" hole. Then peg or bolt across as needed.

24" is still a long way to go. Seems overkill. Even in coastal regions with hurricane winds I think the longest post connection we needed was 18".

The timberlinx can be used for tie downs. There is a connector that screws onto threaded rod. Yo can epoxy the threaded rod into the concrete and the timber connector into the post. In an area of high load they can be doubled up.

I don't think that a plunge cut while felling a tree is a fair comparison to plunging into end grain for "joinery". I've done both and the latter is much more nerve racking, but it is also probably the quickest way to get the job done. The fun part is widening the plunge to allow the 1/2" plate. I understand being hesitant about doing this with a chainsaw, as it requires skill with a chainsaw and understanding of plunging technique.

I wouldn't recommend it for everyone, but a chainsaw makes sense to me.

Tell the engineer to make the anchor round so that an old fashioned round hole will work. Instead of a plate, make it a tubing.
I can't believe we're even contemplating doing this... retarded!

I would first question why 24 inches? That does not seem to be typical, or even something seen in the extreme case. So is this just based on his calculation of shear on the post sections on each side of the bolts? If you need more shear, make the post thicker(flared at the bottom)? Or make things even easier and bolt the anchor on the outside of the post(like the hidden wall side). Recess it into the post so that it is flush with the outside face of the post. Or if on an exposed face, recess it into the post(not centered but offset), and cover it with a well fit 1/2 in thick piece. You'd basically create a long mortice and make a cover. Just some thoughts..
I want to know what the basis is for 24 inches. There is nothing ready made to do that(plunge) because it's not a usual practice, eh? If you were laminating boards to make a post, no problem...