An obvious alternate explanation is that fast-growing malignant cancers are likely to kill you even in the unlikely case that you are able detect them before they are large, whereas slow-growing benign cancers are likely to sit there until you get around to detecting them but are not particularly dangerous in any case.

As I have understood cancer development; benign tumors are not really cancer. But the rise of malignity is an evolutionary process, initial mutation increase division rate / inhibit apoptosis, additional mutation occur down the line + selection for maligmant cells. So one can still identify an early stage of cancer, not necessarily early in time but early in the evolutionary process.

claimed that almost all the studies on early detection of cancer confuse degree of disease at time of detection with "early detection". That is, a typical study assumes that a small cancer must have been caught early, and thus count it as a win for early detection.

But then is real early detection really what we are interested in? If study X shows that method X is able to detect smaller tumors than presciently used method Y, wouldn't we consider it a superior method since it enables us to discover cancer in an earlier stage of development when it has not metastasized?