Both d’s had the experience of going up between 80 to 110 points in sections of the SAT without any additional prep. The more times you take these tests, the more you will see these kinds of discrepancies. And I’m talking about scores going up and down, not a linear pattern of improvement. Also major differences in scores between act and sat. 35 ACT English vs 660 SAT verbal within a week. 35 ACT math vs 650 math (other d-- both tests taken within two weeks if each other. )
So no, don think any one sitting is an accurate account of anything.