When Blueprint default values are edited, those edits will also be propagated to any active instances in the level. Each edit event will mark the level as dirty.
Similarly, in a World Partition map w/ OFPA (one-file-per-actor), external Actor assets will also be marked dirty post-edit. This can lead to significantly large numbers of unsaved assets after a single default value edit, which can make developer workflow difficult.
Since default values are serialized to the CDO, and only per-instance edits are serialized to the level/OFPA assets, there is no need to dirty the level/OFPA assets after default value propagation, as they would not require saving.
This issue is related to [Link Removed], but is unrelated to Blueprint compiler workflow.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-179809 in the post.