Harvey lemon, cold hardiness down to 16F, is it a myth?

[parkerl]

It's been many years since there have been temperatures that low in my area (Zone 8A, North Florida). I have 1 test Harvey tree in the orchard which just successfully produced ripe lemons in 2019. It's on trifoliate root stock. The tree has not suffered cold damage at 27-28 degrees F. When it was smaller (under 5 feet) we protected with frost blankets, but that is the only protection ever given it.