SERVER-114103 and SERVER-114237 will add sampling for the change streams pre-images collection on every step-up. This is restricted to DSC deployments and deployments with the feature flag for replicated truncates enabled.
On ASC, and if the feature flag is disabled the sampling only happens once per node startup (or precisely, every time consistent data becomes available - but it should be relatively rare).

The performance impact of the additional sampling on every stepup should be quantified so we have an idea of how much it will impact stepups.