ECGs can be a bit of a nightmare. 'Abnormalities' are not infrequently benign or caused by artefact but until you do further tests you can't tell the difference between these and the real pathological ones. Some abnormalities are pretty barn door pathological but that is not what these threads are about.
Many medical tests have a high sensitivity (they catch nearly everyone with a disease) but a lower specificity (they include some people who are fine). No test is 100% accurate. At the end of the day, it is better to be over tested and found to be fine than to be mistakenly declared fit only to end up in a smoking hole in the ground due to a problem that could have been found