Why does the windows selector change?

Help Activities
, ,
1

I meet a problem that used screenshot activity, yesterday is：

wnd app=‘explorer.exe’ cls=‘Progman’ title=‘Program Manager’ /
wnd cls=‘SysListView32’ title=‘FolderView’ /

but today is：
wnd app=‘explorer.exe’ cls=‘WorkerW’ idx=‘*’ /
wnd cls=‘SysListView32’ title=‘FolderView’ /

Can someone help explain why?