Just for fun I decided to try installing the Sims 4 using a Sims 3 bottle. Turns out that's all I needed to do - once the Sims 4 was installed, it launched and ran - no questions asked.
The gameplay was a little choppy in my video. The screen resolution was an odd size and I used Simple Screen Recorder to capture the footage which naturally caused a fps hit. But otherwise, it ran great!