Paul, which picture are you referring to with a crimp that appears 1/2" deep?
Of mine, the shell on the left, of the picture of four, is a factory Eley, and it's a tiny bit deeper than mine, but it's a 9/16oz load. It isn't even 1/8", and none of mine are more than .090".
If you mean the one on the Reloaders Net page, that is a slug, with a card. I have no slug experience, and never paid them any attention, but every roll crimped slug I have seen is, as your "old eyes" suggest, about 1/2" (see picture of European 20ga slug)
My Bridgeport 12ga. crimper is convertible from rounded to square, but I leave it as round, as it seems to produce a cleaner crimp on once fired paper.
You may find this link informative.
https://wethearmed.com/reloading-and...vs-fold-crimp/
It doesn't speak specifically to your question regarding possible pressures of 'excessively deep' crimps, but my belief is the crimp only needs to adequately hold the over-shot card in place, not achieve a finished, loaded shell dimension. Plastic crimps won't hold a card permanently in place unless they do a 180, but once it does that, why go deeper?
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