The downside is that if the project decides not to have that in the code, nobody gets it. Example: I suggest to a customer to use it. They decide they don't want it, I can't use it too.
But, there's also nothing stopping you from adding this during development and not committing it.
You could probably accomplish something similar, and possibly inject some rack middleware to add the view, or even mount it as a rails engine.
> NOTE: starting with v0.7.0, it is no longer recommended to add the ruby-lsp to the bundle. The gem will generate a custom bundle in .ruby-lsp/Gemfile which is used to identify the versions of dependencies that should be used for the application (e.g.: the correct RuboCop version).