Yes, the conversion is roughly 1:1 as a crude approximation. So 1000 kJ measured by a power meter is roughly 1000 calories.
this is the problem:
593 calories and 1458 kJ is a completely wacky and wrong conversion. As I understand it, Wahoo bike computers sometimes report wrong conversion, and then Wahoo syncs to Strava/TP/TR and unfortunately Strava and TrainingPeaks trust and use the wrong value.