In the previous version of Android TV, the search button allowed you to access the search function in the program you were in. Pressing it in Youtube would take you to Youtube search, pressing it in the PlayStore would take you to the Playstore search and so on.
On the current version, Android Oreo, the search button always takes you to Google Assistant.
I think that the previous approach was more useful than the Android Oreo approach. What do you think?
I noticed this change too and also much prefer the previous implementation.