Every guide, comparison and detector run we have published under headless.
Old headless Chrome gave itself away through a UA token, empty plugin arrays and zeroed window dimensions, and new headless mode closed most of that. What is left to detect is almost always the absence of a real GPU, not a flag.
A launch that jumps to the front is fine once and unusable in a loop, and going headless to avoid it changes what the page can measure. There is a third option: keep a real, normally sized, visible window and stop only the part that interrupts you.