I don't think that applies to conditional rendering, does it? You can't speculatively execute a graphics API command buffer submission and then dash after it shouting "wait, come back, I didn't mean it". Same with any kind of I/O, I'd think.
You are correct. But the same strategy can be used for optimization. Eg. get rid of the whole if block, and preferably dependencies to make it pure so that it can be further optimized by caching the output. Although cpu can be faster then cache so always measure.
