updating reuseExistingChunk description

Author: chrisdothtml

src/content/plugins/split-chunks-plugin.md

@@ -180,7 +180,7 @@ A module can belong to multiple cache groups. The optimization will prefer the c
 
 `boolean`
 
-Reuse existing chunks instead of creating a new one when modules match exactly.
+If one of your chunks contains only modules that are already going to be split out, it will be reused instead of a new one being generated. This can impact the resulting file name of the chunk.
 
 #### `splitChunks.cacheGroups.test`