Yes, I know the ARB is superior in that regard. That's why I'd prefer it for a newborn.
I still PERSONALLY prefer any kind of rebound control to none-- especially in my vehicle. I think the vehicle dynamics have to be taken into account as well. Rebound control is going to be much more important in trucks, or with kids in the last row of a minivan with a small "trunk" space, or in a small car, than with a child in a larger car or the middle row of a minivan or SUV.
I have never seen a newborn come in in a convertible with RF tethering capability. Most people I see use infant seats. If the infant seat handle is allowed up, I do recommend that, and explain why. (I also let them know whether there are any disallowed positions for the handle, in case they decide not to.) All the newborns in convertibles I've seen were seats with no capacity to tether RFing. If I did see one, though, I would definitely expound both the benefits and risks, and explain that some people are comfortable with it from birth, and some not until the baby is 4, 6, or even 9 months old. I would give them resources for further research if they wished to do it and let them make the choice.
Like I said, I don't usually see babies in convertibles that RF tether at all until 9-11 months.
The SR32s and Keyfits are really popular with the population I see so many of them aren't even moving to convertibles until then. Among seats that RF tether I do see, most are Britaxes, and many of the parents chose them because they can.