The reference to "delay" and "four hours" is confusing (and superfluous). [Again, not to labour the point, but the concept of "delay" plays no part here; case law has led to the interpretation of long delays being handled as a cancellation, but in this case, we are clearly dealing with a simple cancellation. I also don't know where you came up with "four hours" - it seems that you are thinking of the case of when a "long delay" is handled under the regulation as a "cancellation". In the present case, the flight was cancelled, and the offered replacement flight wasn't until several days afterwards - not that calculating the time to that replacement flight matters in any way, given that we are dealing here with a simple and uncontested cancellation]

A cancellation at such short notice automatically requires compensation, except where actual "extraordinary circumstances" can be proven. This applies to all customers on the affected flight - regardless of whether they opt for re-imbursement; regardless of whether they are re-routed without any delay; regardless of whether they are re-routed with delay [which can lead to additional compensation under other Articles]; regardless of whether they are re-booked on another day.

All passengers on a flight that is cancelled at such short notice and which was cancelled for reasons that cannot be justified as "extraordinary circumstances" are due compensation (€600 for this particular flight).