assumed it was a sloppy reference to the shrinking Y

Same. Knowing nothing about “inews,” and given the headline, I figured the article was nonsense and just opened for DOI of the prompting research. But I was wrong. OP’s a brief, non-sensational, accessible summary of a nascent area of epigenomics. Even the headline isn’t made up, just a curious observable phenomenon: older men often have a greater % of cells missing Y.

There might be a built-in clock …. or maybe some mechanism that can detect a certain threshold of mutation

Interesting. Both sound like hypotheses that could be tested experimentally with the help of intersex cohorts with different ratios of X and Y willing to take the LOY blood test, since then a parity check between subgroup medians of LOY-positive subjects would, in theory, suggest if/whether time-based or clearance-based LOY is the operative mechanism behind the phenomenon.