This is simply not true - it assumes that everyone's forwarding server for an unknown record is the root servers directly, which isn't the case.

If this were true, my life would be much easier because DNS propagation would be much more predictable than it is today. One bad server in the chain serving obnoxiously high and invalid TTLs can ruin your day. It's not very common percentage-wise, but it certainly happens every time we switch DNS over for Stack Overflow.