Ok, let me chime in with some explanations.
Under normal circumstances TotalFinder tries to “capture” all new Finder “file browser instances” and convert them into tabs. Finder file browser instance could be a new Finder window or a new native Finder tab - depends on your Finder settings and macOS version. There is one exception, in case of a DMG file, TotalFinder lets Finder do its normal job and does not capture.
TotalFinder does have knowledge of the reasons why new Finder window is being opened and who and how originated it. It just sees new Finder browser created and at that point can decide to capture it.
I have implemented an escape hatch for people who want to opt-out. If you hold SHIFT key during new browser creation TotalFinder will let Finder do its normal job.
For example to open a folder in a new window, you right-click and select
Open in New Window while holding SHIFT. Please note that you have to have unchecked
Open folders in tabs instead of new windows in Finder -> Preferences -> General.
Unfortunately SHIFT interferes with other menu shortcuts. So for example SHIFT+CMD+N does not open new window, but actual menu item takes precedence.
I should consider overriding CMD+N and make it really open new TotalFinder window under all circumstances.