Honda Mech ?????
I really don't want to take this way off topic but ..... I cant believe you are even asking this question if you work at a Honda Dealer. I might be wrong but the only "authorized" repair for modern tires is done with a plug patch from the inside of the tire. I bet if you go to every tire manufacturers web site you will find that all of the kits mentioned below are basically forbidden.
Now if you just want it for an emergency type kit to have in your own car, I could understand it. Maybe ?
Sorry for the rant but it bothers me that my Sister or a good friend could take their car to your shop and have un unsafe repair done. When it comes to anything safety related either do it correctly or don't do it at all.
Just my opinion,
You're correct that the RMA (Rubber Manufacturers Association) guidelines say both the path of the injury and the inner liner should be sealed. Often, that would mean this type of repair.
But tire plugs are not really an unsafe repair. Saying they're unsafe is a little bit of an exaggeration.
One of the tire shops I used to work in installed both plugs and patch/plugs, so I've personally repaired many tires using both methods.
However, these days if I'm paying the shop price for a tire repair I would want a patch plug. I do plug my own tires, though, because I know how to properly use plugs.
And if I were a shop that was concerned about opening myself up to liability, I would probably only install RMA approved repairs and charge customers accordingly. That's not to say patch/plugs are foolproof. They can and do leak because of improper installation or time.