First, products like these unfortunately represent a very poor value. At the end of the day, you're paying about $8 each for... sticks. And not very big sticks, either. The specific issues that hamper this product are:
They aren't a good shape for this purpose. If I had been more analytical before ordering, I could have predicted this. What works well for terrariums, imo, are sticks with crooks and small branches so you can support them on the bottom in at least two places, so they don't roll.
They aren't a good weight for this purpose. These sticks are really light considering their size. Between that and their shape, they are only mediocre for snakes and virtually useless for any lizards larger than brown anoles. They just move and shift too easily, and it's possible an animal could smack itself in the jaw hard if it steps close to one end too vigorously.
Anyway, I would not make the same mistake I did and skip these. You likely have better (and much cheaper) sticks growing outside your window.