Unable to understand behavior of connectors

[visProgrammer]

I am working on Piping and Instrumentation Diagram template in Visio 2013 and unable to understand the behavior of pipelines in it.

I was trying the following steps:
-Create a Major Pipeline (say P1) from Pipelines stencil.
-Create another Major Pipeline (say P2).
-When I connect P2 with P1, P1 will break into P1 and a new pipeline (say P3). After this Visio automatically join all the 3 pipelines with a junction, as shown in image 1 in the attachment.

-Now when I again connect a new pipeline to P1 then same process happens. (i.e. pipeline breaks, junction get created and all pipelines get connected with that junction).
-But when I connect any new pipeline to P3 created earlier, then a instead of breaking pipeline and creation of junction automatically, the new pipeline just get glued to P3.(see image 2 in the attachment)

I am not able to understand why junction is not created while connecting a new pipeline to P3? P3 is created by Visio automatically from P1. Both P1 and P3 have similar properties, sections, formulas and data, then why P3 is behaving differently from P1?

Can anyone help me to figure out what is happening?
Thanks in advance.