The following should explain
If you draw this in your SketchUp 2019
And change from ortho to perspective the whole model space is zoomed out and not focussed in perspective on the smaller block
This wasn’t the case in SketchUp 2018!
I can’t see any difference here from previous versions. The perspective camera and parallel projection camera functions rather differently, and especially the zoom level may vary a lot when you change between them. In perspective mode “zoom” moves the camera back and forth. In parallel projection “zoom” changes the the size of the image plane, without moving the camera in space. Going from one mode to another should give you approximately the same zoom as you had the previous time you used that mode.