At first, I thought Jellal's arc copied the Rave Master Arc where King and Haru's dad fought, mostly because of the tower. But damn. Good notice. But to me, the main difference is 'willingness'. Jellal does this under someone else's control, and spends a ton of time wallowing in guilt. Sieghart willingly harms Elie for a misguided form of justice, and actively works to repent.



PS, Natsu does not actually save Erza. So it's more 'the method of saving the girl' doesn't match.