Why is my Machining Allowance surrounding one volume not connected to each other?

Machining Allowances are added to the structure to guarantee enough material for post processing steps after the manufacturing of the design. When creating Machining Allowances each functional face is selected, depending on the settings can result in these two different Machining Allowances:

The first picture shows the selection while the automatic creation is activated and one face is selected at a time.

The second picture shows the selection while either the control key was used or the automatic creation of Machining Allowances is deactivated. In this case it is clear for the software that the selected Machining Allowances belong together and therefore need to be connected.