... the actual version 4.1.2 seams to have a problem with the settings of the infill to be print every (1) layer.
I have set (1) every layer by using 2 different angles.
But it prints only one line direction for 1 layer and the 2nd angle while printing the next upper layer.
I can't say when this issue was coming in, the version 4.0 also doesn't execute two angles into one layer but always when set 90 / -90° . It wasn't important for me because i used always bottom- and top layers. Now I had to print a flat part without bottom and top layer and so I could see this real bad quality inside.
Yes, a solid infill such as bottom and top layer are printed like infill at 100% but there are some differences with speed, direction, retracts a.s.o. Printing infill doesn't retract the material, so the print will get dirty inside. For real proper printing a grid it needs to consider it when drawing the model.
You can test it out by setting NO bottom and NO top layer but infill 100%. I have never tested it.