Hi Zach,
This behavior change started with windows RS3 update,
In RS3, windows will start browsers upon window startup if they had background process.
The SBA4B (browser extension) architecture is using background pages for the extension engine,
the background processes remains running even if the browser is being closed.
This implies that windows will start the Chrome\IE browser on startup, unless the user will manually close the IE\Chrome processes (e.g. using task manager).
For Chrome browser, this issue can be workaround by the following:
1. open Chrome browser
2. navigate to "chrome://settings/"
3. search for "background" and find the "Continue running background apps when Google Chrome is closed"
4. disable the "Continue running background apps when Google Chrome is closed" option.
For IE there is currently no such workaround, and this is a limitation