Question Unity2021.1.13f1 AssetBundle.Unload(true) memory leak?

I am sure，I unload all assetbundle rightly！My UNITY VERSION 2021.1.13f1

I do a test on android
I load lots of assetbundle，then i unload them
i find that，
When i start my app， the memory is 258M （privateOther 56M）
When i load all assetbundle，the memory is 500M（privateOther 310M）
When i unload all assetbundle，the memory is 393M（privateOther 182M）
Is this a memory LEAK？

I do a another test
I instantiate a lot of prefab in assetbundle ，and destroy instance and asset，and unload all assetbundle
I FIND THAT
more i load，more memory remain when i unload
Is this a memory leak？

 

Anyone help?