In the block manager, the checkbox is called “Block Preview”. If unchecked, there shouldn’t be a preview! With very complex blocks, it can take a very long time to create that preview. That is why I leave it unchecked.
I see what you are saying with regard to the auto-update on the Named View - it won’t update when geometry is moved. However, I have the same problem that views can take a very long time to refresh with complex geometry and/or multiple views. I know about the list view mode, but prefer the thumbnails. I can understand if they refresh on block changes, but still would prefer they didn’t unless auto-update is checked.