The biggest problem with this statement is that there are no regulations for aftermarket products, thus there is no specific CMVSS regulation that the bundle me is passing.
The primary standard that determines whether or not a rf'ing seat meets standards is how far downward the seat rotates during crash testing. The maximum rotation allowed is 70* measured from verticle - anything less than that and the seat passes dynamic standards.
So basically, unless you're pushing the weight limit of the seat by adding the bundle me, the seat won't fail CMVSS 213 dynamic testing from the addition of the bundle me. This speaks nothing of how the harness is fitting the crash test dummy though - whether the bundle bag is bunching and a real live baby would be screaming due to the fabric being pulled into them in order to have the harness anywhere near tight enough.. whether the straps are laying flat, whether they're in the right position, etc. etc.
The other thing that factors in, is that CMVSS regulations regulate the amount of padding used in carseat covers. Adding a bundle bag is going to change the amount of padding under the bum, which would affect the overall seat, but still wouldn't affect the dynamic testing which is specifically what those letters are referring to.
So the long and the short of it is that that letter is put in there to assuage parents into believing it doesn't matter what manufacturers, CPST's, or Transport Canada says, and that it's ok to use. It's meaningless in terms of technicality, but the average parent doesn't know that, and uses the bag believing that it's safe to use. Maybe manufacturers should focus on developing a better solution for keeping infants warm in carseats instead of pushing something that isn't safe onto parents and telling them it's safe...
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