this did not work for me.
new blocked state: true even after doing
pm block com.sonymobile.advancedwidget.entrance
reboot
several time.
The state should be "new blocked state: true" after running "pm block com.sonymobile.advancedwidget.entrance" so the command has been successful. Repeating the same command does not toggle the value.
(To reverse you should run "pm unblock com.sonymobile.advancedwidget.entrance" and then the state should be "new blocked state: false")
To check if the command has worked after reboot, on the home screen slide from the homebutton (the house) upwards, if you only have the google now symbol all is as expected. If you still have both "google now" and "what's new", something is wrong. Also the "What's new" app should not be visible anymore in the app drawer.