From what I've investigated so far, webpack likes to use the webpack:// pseudo-protocol for file references in most of its Source Map modes, including its defaults, and from what I've seen that seems to be the single biggest issue of cross-browser Source Map compatibility in the webpack ecosystem (other ecosystems have different problems). Chrome seems to be able to figure things out from the pseudo-protocol in just about all cases, but Edge and Firefox seem to be confused more often than not.

In some cases it looks like Chrome takes extra efforts to find physical files on disk from bad URLs, and in other cases Chrome does more with virtual file structures included in the same bundles (the webpack:// pseudo-URLs often point to other "sections" of the same JS bundle) creating a virtual file tree from them that looks close enough to the on-disk file tree as to seem effectively the same to many developers.