Sweep from face of extrusion fails

Why does this work
```python
import cadquery as cq
PDI = 4.
PDO = 8.
PDL = 20.
path = cq.Workplane('YZ').moveTo(0,PDL/3).lineTo(0,2*PDL/3)
port = cq.Workplane('XY').workplane(offset=PDL/3).circle(PDO/2).workplane(offset=PDL/3).circle(PDI/2).sweep(path, multisection=True)
show_object(port)
```
and this does not?
```python
import cadquery as cq
PDI = 4.
PDO = 8.
PDL = 20.
s_shell = cq.Workplane('XY').box(8, 122, 62)
port = s_shell.faces('>Z').circle(PDO/2).extrude(PDL/3)
path = cq.Workplane('YZ').moveTo(0,PDL/3).lineTo(0,2*PDL/3)
port = port.faces('>Z').workplane().circle(PDO/2).workplane(offset=PDL/3).circle(PDI/2).sweep(path, multisection=True)
show_object(port)
```
anything obvious I missed here?