Outline stroke doesn't act the same from menu or appearance effects

Hi y’all

Here is the thing :

Converting a stroke into a shape is not a problem from the Object menu > Path > Outline stroke

But when I try to do the same via the Appearance panel > Effects > Path > Outline stroke there is no visible result. Same with the menu Effects > Path > Outline stroke…

The line stays a line.

I would love to learn how these appearance effects work

If you have any clue feel free to share

Thx

Didier