Here is the capx:
-There are 2 tileSet objects, they both belong to the bulletFamily.
-The bulletFamily has a bullet behavior.
-Only blockB has an aditional Jumpthru behavior.
-On start of layout I set the family bullet speed to 100.
Then preview, resut:
blockB (the one with jumpthru) has dobuble speed than blockA
If you think this is a bug let me know so I post this on the bug section.