I bought an OSEPP 16x2 LCD display shield today (16X2SHD-01) and found it has the same issue. The test sketch posted here reports it as "BAD". There is a 1K pullup resistor and no base resistor (schematic from OSEPP). Intriguingly, I can just barely see an empty SMD outline next to the 1K resistor. I tried removing the display to see how easy it would be to add a base resistor, but failed: my only desoldering tool is a solder sucker and some pads were starting to lift. So I'll live with it for now: I don't really need to control the brightness for the simple projects I have in mind.