[2019] Reinforcing a friend directly from Freeplay.

So the other day my cousin was doing a contract and I was running around in freeplay. Suddenly i get a visual alert that there is an even close. I turn in that direction and it seems pretty far so I open the map and the alert (the purple whatchacall it displays my cousins name) I forgot what I did and boom I start loading up. I just thought i gotten kicked out of the game due to a bug but nope suddenly the game is leading me towards a mission and my cousin and his team are by my side and we are in a squad. I know I didn't accept an invitation from him and he didn't even notice I was part of the contract until the end.

Has anyone experienced something similar? is that a feature? I don't have time for free plat or that many playing friends or family to play with so it was the first time it I seen that.