Yeah, I don’t think any of this is odd at all, and
Carbonfiberboy summed it up succinctly: HR varies. Further, the essential nature of sports performance is variability. The important thing is not wattage/HR variances between performances, but rather that your training is hard enough to force physiological adaptation and to allow you to recover and be fresh for peak performances when you want to do them. Training is not a straight line between where you were, are, and want to be, not ever.