Just today I noticed your update note for 10.3 that said the Explorer demo now allowed selecting the columns to display, so I tried it.
The attached images show the same files. Initially I just selected the properties column for display. The other two images show what happens if I click on the Properties column to sort or if I just wave the mouse over the window. The properties will change back and forth between the 3 sets of values displayed, depending on sort or waving the mouse.
We seem to have a partial fix. The .JPG and .TIF files now retain the same dimensions when I toggle the properties column to sort up and down. The PDF file continues to switch back and forth between the values displayed in my image, and the mouse will sometimes cause the change if I just wave it across the column. Oddly, at times the dimensions for the .JPG file are also listed for the .PDF file. Then if I wave the mouse over the PDF file, it changes to 25x25.