When I read about it, I couldn't understand it either. They didn't explain precisely, but IIRC, it was a pistol with a tactical light, which explains why there might be more space that usual. I couldn't find the particular incident, however.
This sort of thing is unfortunately somewhat common:
The sig p320 thing isn't about safeties at all but a mechanical design flaw that the company has remedied with a recall. And that safariland link just seems like safariland is a terrible manufacturer of holsters.
If this is the one I’m thinking of it was pretty clear that there was a police department that was incompetent and blaming negligent discharges on the firearm instead of on true officers.