It’s fairly simple. The Saltlake satellite is much newer than the others. Which means it doesn’t have nearly as much data stored on existing nodes. Therefor the data you have received on your node represents a much bigger piece of the pie compared to other satellites. And because satellites audit a random piece every time, the larger your piece of the pie, the more audits you get.
This is exactly what is expected. You’re getting the benefit of one satellite being new, the others represent more how long it would normally take.