It does matter. I started using a iPhone maybe a couple of years back, after using an Android phone for many many years, and I still find out stuff randomly by chance that they could have just told me about.
Biggest example when I just got the phone, took me maybe a couple of days before I understood that swiping from the top of the screen and down depends on if you're on the left side or right side of the phone, which decides if you see the notifications vs the "control panel" thing. Initially it felt random which one it showed.
And I'm a technical user, probably in the top 1% when it comes to technical knowledge compared to the rest of the userbase of iPhones. And how do you think things like that works out for the rest of the people who don't work with technology for a living?
My mom didn’t ask about it until after the first year.
So to answer your question… maybe it doesn’t take to be the top 1% of something.
But the good, old Apple troubleshooting works: nuke it, and start again. If I close the app and restart it, then it's back to its single window form.
Oh, well.
So, after an onboarding workflow, in other words. What's the difference between giving them a quick intro, and their being some form of onboarding built into the application? Consider people who don't have someone on hand to introduce them to the product: how should they gain that same level of competence?