[Minions] Minions went behind nexus instead of going to the nexus turrets

I was playing GP in a custom game and destroyed the bottom lane inhibitor and the nexus turret to the right. I was on blue team. However, instead of the minions heading towards the other nexus turret, the minions went directly to the nexus and went behind it. There is a replay file above. The minions only went to the nexus turret on the left after enemy top lane minions spawned. Is this a bug or is it the way minions are supposed to work when burst aoe waveclearing happens.

Link: file:///C:/Users/JUSTIN%20ADMIN/Documents/League%20of%20Legends/Highlights/7-7_NA1-2474261959_01.webm

PS: It is a practice tool game.

Thanks for wasting your precious time to look at this text.