Extrusion and follow me issue

Hi all, when I extrude this shape I get the result I want. Namely, that all the surfaces are intact.

However, if I take that same shape and extrude with “follow me” it around the central object, I lose the bottom surface.

Any thoughts as to why?

Any extrusion on a face will remove the face, conversely if there is no face it will create one.

Edit: I see what you are asking now, why the different face treatment with follow me.