[BUG] Switching back to npm 6 from npm 7 results in install error

Current Behavior:

I believe npm 7 is meant to be fully backwards compatible with npm 6 but I'm seeing some slight changes in my package-lock.json when I switch between the two that is causing an install error.

This is an example I'm seeing in package-lock.json under dependencies for this library:

npm 6 correct format:

    "webpack-raphael": {
      "version": "2.1.4",
      "resolved": "https://registry.npmjs.org/webpack-raphael/-/webpack-raphael-2.1.4.tgz",
      "integrity": "sha1-urmFNtYox2zSQcuj0KbMdkszBD4=",
      "requires": {
        "eve": "git://github.com/adobe-webplatform/eve.git#eef80ed"
      }
    },

npm 7 format:

    "node_modules/webpack-raphael": {
      "version": "2.1.4",
      "resolved": "https://registry.npmjs.org/webpack-raphael/-/webpack-raphael-2.1.4.tgz",
      "integrity": "sha1-urmFNtYox2zSQcuj0KbMdkszBD4=",
      "dependencies": {
        "eve": "git://github.com/adobe-webplatform/eve.git#eef80ed"
      }
    },

installing using npm 7 format package-lock, but in npm 6 (I'm on 6.14.0) will generate a new package-lock in npm 6 format, but changes the format of the git source for certain dependencies. i.e. "git://github.com/adobe-webplatform/eve.git#eef80ed" becomes "eve@git://github.com/adobe-webplatform/eve.git#eef80ed":

   "webpack-raphael": {
      "version": "2.1.4",
      "resolved": "https://registry.npmjs.org/webpack-raphael/-/webpack-raphael-2.1.4.tgz",
      "integrity": "sha1-urmFNtYox2zSQcuj0KbMdkszBD4=",
      "requires": {
        "eve": "eve@git://github.com/adobe-webplatform/eve.git#eef80ed"
      }
    },

now if I delete my node_modules and try installing in npm 6 from this new package-lock, I get the following error:

npm ERR! code ENOLOCAL
npm ERR! Could not install from "node_modules/webpack-raphael/eve@git:/github.com/adobe-webplatform/eve.git#eef80ed" as it does not contain a package.json file.

Expected Behavior:

npm i using v6 should generate package-lock.json format into correct v6 format without having to delete the package-lock file first

Steps To Reproduce:

1. start with v7 package-lock
2. switch to npm 6 and npm i which updates package-lock.json
3. npm i again using the new package-lock.json

Environment:

• OS: Ubuntu 18.04
• Node: 12.22.1
• npm: 6.14.0

Start with the package-lock.json examples and reproduce the reported sequence: use an npm 7 lockfile, run npm i with npm 6.14.0, then run npm i again after deleting node_modules. Trace how the git dependency is rewritten under dependencies/requires; done means npm 6 installs successfully from the generated v6 lockfile without the ENOLOCAL error.