Why is model slice generation not supported with an inport as starting point?

Matlab 2015a introduced the Model Slice tool as part of SDV. Why is it that using an inport block as a starting point is not supported? The documentation states that it is due to the fact that it is a virtual block, but I don't understand the rationale behind why that makes it impossible to start a trace from that point. Does anyone have any insight why virtual blocks are treated in this manner?

Answer 1

[Monika Jaskolka]

I will answer my own question (somewhat). The reason for this is not known, however, SDV 2016a now allows inports to be used as starting points.