I'm working on Blender Guru's anvil tutorial. At this point he insets a face and uses the boarder option to achieve the desired result. I'm using v2.9 which no longer supports the B shortcut, but I can enable it in the new sub-menu for the command. Nevertheless, nothing happens and the boarder piece remains, so I can't perform the extrude on a single entity; it comes out as two spikes. What am I doing wrong?
I actually encountered the same issue, and wasn't even working after trying @emir process (on the answer). The only way I found was to move the inset face until it snapped the central edge. I haven't finished the anvil yet so i don't know if it will cause me problems, but for the moment it's OK