Rarely, unmodified Niagara will cause diffs and bloat the patch.

Attached is a project that picks up Niagara from the content sample.
The probability of reproduction is about 1/10.
The simpler the project, the lower the reproduction probability.
I am attaching a .bat for easy reproduction.
Please rewrite the engine path to use it.

We have also seen this problem in UE5main, but the call stack where the difference occurs is not the same, so it may be a different issue.

In UE5main, Niagara seems to almost always generate a diff.

.bat should be placed on the same level as CookNiagara.uproject.
When using UE5, the patch path will change because IOstore is enabled by default.
You need to disable IOstore and modify the path to WindowsNoEditor->Windows.

patch_diff.bat
After creating releaseversion and patch, output the contents of patch to csv.
If the problem reproduces, the csv contains the unmodified Niagara assets. (patch20220502082500.csv)

cook_diff.bat
You can use -DiffOnly to see which assets are diffing, memory offsets, and call stacks.

1. Create a content sample package with 4.27.2.
2. Create a patch without changing anything.

Ideally, the patch should contain nothing, but in rare cases it will contain Niagara assets.
(There are some levels and assets that will always be included in the patch, but they do not matter.)