PQ/M working with list syntax - List.RemoveItems with criteria

As Australians like to say - you're a legend!. This syntax makes perfect sense now. The use of the {} for the list2 part of the List.RemoveMatchingItems clinched it - as was the simple reference to the [Lists including Rev] for list1. 

Thank you so much for the patience to explain this scenario. 

As a mild tangent to reducing steps in PQ - can I ask how to attempt the same (removing items in a list) in the same column rather than adding a new one? Or is that not necessary (because we can add steps to remove)? Thansk again.