Archie, you're so wise in so many ways that I would agree with you if I didn't know differently.
I wore the same brand and style of athletic walking shoe for at least 17 years. I started out with a size 10B. Over the course of time, my big toe started bumping the end of the shoe with each step. Because women's shoes are incredibly hard to find in size 10 1/2, I tried a 10W. It didn't work. My toe still bumped, and the extra width provided no support to my heel and middle foot. By a stroke of luck, I was able to locat a retailer that carried that exact shoe in a 10 1/2B. That was the size I needed, so I was all set for another 6 years or so.
Repeat story... except to say that size 11 is much easier to find. I now wear that very same shoe in an 11B. The width has not changed; only the length has.
I'm living proof that length can increase with age as well as width.
My husband has had the same experience, having worn the same manufacturer's work boots for decades. He wore a 12D in his youth; he wears a 13D now in that brand. In another manufacturer's athletic style, he has gone from a 13D to a 14D within the past five years. Again, change in length, not width.
Now, I'm sure there are explanations other than the bones put on more growth. Tendons and ligaments loosen with age... lord don't I know that!... and so spread probably occurs just as often in length as width. I just happen to believe that it occurs to everyone, regardless of thyroid status.