It's Valve teaching you to not watch for those, but to check your CS inventory. wp volvo lol
But yeah to be serious nope It doesn't notify about drops.. but it should.. they should add a special notificaton just for major drop being more of thing and making you enjoy it happening in real time..
A variant of the EVENT notification groups can make appear could be used, so even if you don't see it for the time it is shown, theres that window on the desktop that won't go away :) have it say that you are helping esports or something ? haha they could do a few things that say thanks to community watching major. here have something you got lucky !