For our own cars I have been using tire plugs since bias ply tire days. Plugs are not 100% reliable but they are close to that. The worst that has happened to me is that a slow leak developed at the plug and the answer for that was two plugs in one instance and a new plug in the other. For me, plugs last for the life of the tread.
I get the concept of sealing the inner liner with a mushroom plug or a patch but not doing that has not resulted in trouble for our tires.
The Rubber Mfr’s. Assn. advice leans toward caution and if followed, will result in more tire sales and should help to keep them from becoming involved in lawsuits…