It's totally plausible to do a strict curl without a wall. At the gym tonight, I picked up a 20 pound barbell and strict curled it without moving my upper body at all. That automatically proves that one can do a strict curl without a wall.
Using a wall for a strict curl allows you to use more weight because it's providing support for the movement--that is, you can brace yourself and tense yourself and the wall will keep you straight--try that same weight without a wall and you will learn real quickly that the weight is actually too heavy for a strict curl.
It would seem that a true strict curl would be not to use a wall and only move your arms from the start to the finish position, which would be exceptionally hard, but not impossible, without the bracing of a wall. I suspect that most peoples weights on the strict curl would drop at least 25+ pounds ore more without a wall.
I am not too sure why BHANKS cannot understand this.