Stan, I read your post and another posts from this subject. I cultivate coffee tree at home (and sometimes in garden when weather is hot) many years. I think you have a very favorable microclimate. Probably you live close to the ocean that acts as a heater with thermostat. Talking about frost/cofea - coffee (any variety), of course, it does not tolerate frost that lasts many hours. It will kill this species for 100%
I checked a couple of times as well as behaving coffee tree after a night in temperatures below + 6 / + 8 degrees Celsius. After the first night lasted about 10-12 hours when the plant is in a temperature range of +1 to +5 Celsius there are damaged leaves. Second night the tree usually do not survive. The survival of the whole, long cold nights (even if it was only -1 degrees Celsius is not an option).
Probably your plant was exposed to the cold for a very short time. There are situations when suddenly (for short time) temperature drops from +5 the to -1 C. Probably 15 or 20 minutes small frost will not damage her, but that does not mean that it is resistant to frost. Anyway, what can I say, if your plant is really resistant to prolonged frost you through be or you already are millionaire;) Regards. Dominik