Show as expanded option doesn't work if menu item is created through View.
Steps to reproduce.
1. Create a view with page display
3. Edit the view and add menu item. Under settings check "Show as expanded".
item.is_expanded should be set to TRUE (can be examined through template for ex: menu--main.html.twig
item.is_expanded is set to FALSE
Also tried to edit this menu item directly through Administration Structure Menus and set "Show as expanded". In both cases value is saved but not rendered correctly in Twig. This only happens for menu items created through Views module, if I create menu item manually then it works correctly.