Correct, polarization is key
Hi, first post here, not the most exciting... but:
You are correct. LCD's have two polarizing filters in them, one on each side of the liquid crystals. Light from the backlight is polarized in one direction, "spun" by the crystals depending on their charged state, and re-filtered by a second filter in front. Somewhere in this sandwich, there's also a color filter involved, but I fail to remember in which layer it lies (I'm not sure it's important).
The amount that the polarized light is "spun" determines its final intensity as it passes through the second filter. One of the reasons LCD's are so inefficient is that the primary color filter immediately cuts intensity to 33% (dividing into R,G,B) and then each polarizing filter (even when the light is perfectly aligned for both) cuts another significant chunk, something like 5-10% each. The resulting light is a mere fraction of the original source backlight.
I suppose different manufacturers might put their polarizing filters in different directions. I'm not sure if one orientation or another would pose any benefits.