HotLine, you and I are going to have to agree to disagree regarding the 'history' of TR devices.
Prior to the NEC requirement, so-called 'safety' devices were not marked "TR,' and there were no industry specs regarding just what such a thing was.
Child care regulators had their own ideas, and enforced their own rules. Often they wanted to see either the twist-type faces (which are made in both device and cover plate versions) or plastic caps inserted into every accessible receptacle. Yet, these gizmos were strictly marketing options- there was no standard or certification relied upon.
The same situation, oddly enough, applies to the various claims regarding 'commercial grade' and 'specification grade' devices; the words are legally meaningless, and completely unenforceable.
Let these examples remind us all of just how well the market can work- IF we let it!
