To my understanding, Planck time describes a limit on sample rate, not frequency. That is, we can't perceive time at a finer grain than whole multiples of Planc

To my understanding, Planck time describes a limit on sample rate, not frequency. That is, we can't perceive time at a finer grain than whole multiples of Planck time. But even starting with only integers, we can theorize and simulate floats. The speed of light is as arbitrary a scale as anything else when you're talking about absolutes, hence "it's all relative".