アセットバンドル内にタイプに関する情報を入れないようにします。
Specifying this flag will make an AssetBundle susceptible to script or Unity version changes, but will make the file smaller and a bit faster to load.
This flag affects only AssetBundles for platforms that have type information included by default.
Type information must be present for Web platforms, therefore Unity will reject to build an AssetBundle if you specify this flag when building for BuildTarget.WebPlayer, for example.
関連情報: BuildPipeline.BuildAssetBundle