I think it's just a semantic distinction, not a substantive one. The relevant thing is indeed that Webpack is generally used as part of another build process.
OK let's go with your definition. You're saying that "endpoints" may pin their dependencies, but any package that is depended upon by some other package should not in turn pin its own dependencies. ITT, I don't see support for this proposition. 'rigaspapas observed that the problems described in TFA could have been avoided through pinning. Presumably you're thinking of other problems that could be caused by pinning, but why would you think those problems are any worse than causing the program to completely fail to accomplish anything?
Diamonds are more common because node unlike many environments is absolutely tolerant of them. Maybe this "wastes" some disk space, but otherwise this is not a problem. It is orthogonal to actual problems like bugs in particular package versions.
