I can definitely see what you mean, and I appreciate the detailed post!
As for your scenario, I feel as though my heart rate would go up to a moderate amount, maybe less depending on the exact structure of the project.
The reason I say that is because I’ve done similar things in the past. My wife also has a job as a junior developer (working from home as part of a smaller multi-dev team supporting a massive project), but her team is set up in a way that she can only get a few minutes a week with her senior since he is always busy with his own tasks. She was never given documentation or even a walkthrough to explain how their project is structured or how their database is structured (they said in the interview that they would do this, but in reality the senior has to spend all of his time on other projects or in meetings). There are times that she gets stuck on a task that she has been assigned because she doesn’t know where in the source code she needs to look and she can’t get a hold of her senior. She’ll ask me for advice (without looking at the code, it’s essentially a 20-questions type scenario of hypotheticals) and, even though it is a completely different programming language and I haven’t actually seen the code, I can figure out what it is that she is needing to do and help guide her to where she needs to go in her project. When she finally gets a chance to talk to her senior about it a few days later, he confirms that the steps she ended up taking were correct for their set up.
For example, she once had to update the items in a drop down that she couldn’t find in the code in their project. She knew that the dropdown was being loaded on a specific page, but the items weren’t being populated in that same place. I assumed that this was likely using a stored procedure or a view on their database to pull the dropdown items. With that assumption, I was able to help her trace to where the data was being loaded in their data repository. That gave her the name of a stored procedure. She went and updated the stored procedure’s definition in their dev server and it corrected the dropdown. She later met with her senior and he confirmed that the dropdown (and many other features in the app like the dropdown) are pulling out of stored procedures so they don’t have to redeploy code to update things like that.
Similarly, one of the projects I had to work on at my org is actually taking an MVC web application and an API web application that are written by one of their multi-dev teams that are provided by our ERP software provider that we can customize to meet our specific needs. I did have some documentation to go off of, but I was able to get that loaded in and making customizations that fit within their architectural style within a couple of hours when I first started it.