This is sometimes true for early stage projects. There are exceptions, sometimes you can have an engineer creating a library or a framework without any need. An existing library would have done a better job faster, but that engineer just wanted to make a new one. As a result you can have a massive framework, known only by that engineer in which that engineer is very effective. But no one else is. And overall it is a liability, if compared to an existing framework.

In general, the more code you have the more code you have to maintain and massive codebase churned out by a single engineer is more often a liability, not an asset.