Often I find myself fixing a failed rail of an arm chair or a part of a sofa that is inserted between plywood walls and holds the legs. Something like this, those red circles are butt joints where end grain of a front rail meets 2 sheets of plywood.
Now because most furniture is made the way it is made 90% of the time that joint consists of a spit of wood glue with a few 2-3 inch staples applied from the outside that goes through the plywood into the end grain.
I work on location so repair needs to be quick and the joint is hidden so I am not planning to use any kind of joinery that requires hand cutting. But stability is of course a factor given the fact that often that railing is what the legs are screwed into and it being a chair.
Typical repair is remove the dried out dab of glue do a good application covering entire surface make sure it's a good fit and put in a few screw from the outside in to replace the staples.
Now I realize that traditionally this is not a strong joint, but it does hold well (so does the Chinese dab of glue and a few staples to be honest since that's how 90% of factory furniture is made). But I would like to do my repairs as strong as possible.
So my question is, is it advisable to switch to pocket holes for this type of repair? Is there significant structural improvement? It is relatively quick to do and inexpensive.
I watched a few joinery overviews and my takeaway was that aside from cutting mortises which are not time feasible and a few other hand cut joinery the only 2 good fast and dirty options were pocket screws and Festool dominos (with dowels and splices performing about the same as just glue).
What threw me off was this video https://www.youtube.com/watch?v=ERXdLDudBnw
In which typical butt joint screws outperformed pocket hole screws like so:
Is there an explanation of why that happened in this particular experiment? Is this an anomaly?
P.S. This post is about pocket hole screws and I want to keep it on point but as a follow up in your opinion does adding either metal corner braces or gluing in wood braces in the inner corner further improve stability? Or is it a waste of time?