It's always been a thing at away days but it's always transfered from the concourse to the stands then back, then back again. Was often a great way of spreading new songs. Nowadays though, the concourse singing at away ends is almost exclusively for social media content and it rarely transfers to the stands. Sad but that's football now.
We’ve sung in concourses for as long as I can remember, can’t believe someone has an issue with it! Throwing beer is an odd one though, was going on well before the Euros.