Safari 10 Preference Issue

Hi everyone

My macbook pro is running OS El X Capitan 10.11.6 and Safari 10

In the Safari Preferences, General tab, for "New Windows Open With" and "New Tabs Open With" parts:

I can set these two separately in previous Safari version. For instance, New Windows Open With: Top Sites. New Tabs Open With: Favorites.

However, after I upgraded the system to the newest version, I found out these two can not be set separately.

When I choose "New Windows Open With: Top Sites", "New Tabs Open With" will automatically change to Top Sites and vice versa.

Is this a system bug or is it that Apple changed the way it was forever?

Just wandering...

Thanks for your time and help.

Best

Ashton