Regarding replacements, I personally don't see how replacing one or two receptacles with TR's while the rest of the house remains non-TR is going to minimize any hazard unless total replacement with TR is required.
My guess is that the thought process is that eventually all receptacles will need replacement, so gradually over time they will all be TR in dwelling units. However, in the interim, that will leave many dwelling units with a combination of TR and non-TR as they are replaced piece meal over time, which does not negate any hazard.
This appears to be a gray area as far as safety is concerned, but since the code cannot mandate "ex post facto" changes, this is the best they can do.