关于pip依赖管理类型及实际机制的技术问询

最近我看到一种关于pip依赖安装机制的说法，具体内容如下：

Pip installs dependencies using a recursive serial loop. Pip does not check to see if all of the dependencies of all packages are met at the same time.

If the packages installed earlier in the order have incompatible dependencies with versions that are different from the ones installed later in the order, the environment is broken, and most importantly, this problem goes undiscovered until you notice some unusual errors.

我有点不确定这个说法是不是准确，想搞清楚pip到底是怎么开展包管理工作的。

之后我去查了pip的官方文档，找到了和「依赖解析」相关的内容，描述如下：

At the start of a pip install run, pip does not have all the dependency information of the requested packages. It needs to work out the dependencies of the requested packages, the dependencies of those dependencies, and so on. Over the course of the dependency resolution process, pip will need to download distribution files of the packages which are used to get the dependencies of a package.

这段文档描述看起来和之前的说法方向一致——好像pip只是从目标安装包开始逐层梳理依赖结构，并没有去检查整个环境的依赖兼容性，但我还是没法完全确定，想寻求更明确的解答。

备注：内容来源于stack exchange，提问作者An old man in the sea.