Think about the story of the fight. Going into the fight the narrative is that Spence is the bigger guy and will bulky Mikey into submission. If Mikey survives 12 rounds it seems like a good achievement. So if Mikey can make the fight any way competitive what happens? The judges will see anything less than a dominant Spence win as a Mikey win. It's natural when the story of the fight is like this. See Canelo Vs GGG 2 for an example.