The marquee for the large rectangle shows that it is a group of items. Will your objective be gained if you ungroup that rectangle and boolean the portions required?
The rectangle had one unjoined vector in it that was hidden since the entire object was grouped. So evidently the booleans only are active if both selected shapes are closed vectors. Except for the Weld which does not seem to care about it.
Weld is a little less strict in how it handles things. I recently added a check to make sure that all the sources are closed shapes to the boolean ops because a couple people were trying to boolean a line with a shape, and confused that the output wasn’t what they were expecting. I might set the weld operation to work the same way, since it technically has the same restrictions. Open shapes are just ignored when welding.
