Maybe you meant to say was "impossible to launch"?
All I can say is that ante-update it could open a window when launched in incognito mode. But I am not sure if the launched window was or not an incognito window itself (since there was no bar or tools appearing whatsoever).
What I meant is not the option to launch or not an incognito window instance in which to scrape. But to launch or not a window with full extensions and tools (such as it happens now) or without (such as how it was opened pre-update).
Maybe there is a good reason behind why the window that now opens has full navigation bar and everything?