A fact: last fall I had to replace the heads on my ride. due to the coolant was going somewhere but not in the oil, the oil was not going into the coolant either. Seems that there was a microscopic crack in each head, that was only leaking coolant after warm up, and was not smoking, nor flowing . leaking just enough that I needed to add coolant after 500 miles or so. And dripping very slowly from the tail pipe. Would go into the combustion chamber out the exhaust valve, into the cat, through the muffler and drip every 2 to 3 minutes at the tail pipe. A very slow leak but still a leak in the cylinder heads. This stumped many " professional techs". But With my 50 plus years experience with vehicle repair, and some mechanical intelligence and insight I got it corrected. Yes I saw where you stated that you had a "DEGREE" in automotive repair. So do I plus more than likely a few years more experience, I have seen things that many people have not even thought of happening to the automobile. So as I said not necessarily! ED
I've seen things like this happen too. However, a properly used emissions tester will ALWAYS sniff out the hydrocarbons in the coolant. Because the pressure caused by combustion in the suspect cylinder will ALWAYS push back through the same crack that the coolant may be using to get into the cylinder. And there will always be more pressure pushed back through that crack during a combustion event than coolant coming back simply due to the huge pressure differential present. Saw a ton of them on 3.0 2 valve v6's. 5 minute test with an exhaust sniffer will always show even the tiniest crack.
In response to the OP's question, if it seems to be running fine, I wouldn't worry one bit.