Answer:

Yes, AutoPIPE Vessel automatically considers the cone-shell junction as line of support for external pressure calculations.

If the junction is not sufficient then a stiffener is automatically added.
This is clearly printed out in the report (see “External pressure” + “conical junction”).

Observe the vertical vessel with a conical transition section at the middle. The stiffener has been automatically added.

The design report shows inclusion of cone-shell junction as line of support for external pressure calculations.

Also Appendix 1-8 calculations performed to check the design for external pressure for conical shell: