Why exposed filter doesn't appear, when ajax is off in block view
Simply because it is not a page. If you notice on page view, with ajax off, you will see a parameter passes through the url. 

/example?something=yes


If you go to that url directly, it automatically filters your value. 

Since blocks are not pages (do not have urls), you cannot do that. Therefore, reloading the block with AJAX is the only option for exposed filters in blocks.