Yeah it's actually a unpopular opinion
That would be utter disgusting stepson craving for stepmother and it's not like king had abused the mc in 1st timeline
They are Royal imagine a cp marrying his stepmother and she also not a concubine but a proper queen (2nd though) it's good that they got second chance
it's not like she was his stepmother fr though, he refused to call or acknowledge her as that, didn't he? her actions were more like an enemy's than a stepmother's. he had feelings for her in timeline one and offered her to run away with him (marriage isn't the only ending for a couple and timeline 1 sidis doesn't even want to be king lol "i never desired the throne"). i don't think it would be "disgusting" because she never developed that kind of bond with him nor is she at the age to be his mother. having the story stay in timeline 1 would just be a disturbing and darker version of the story and far more interesting than the overused back in time trope
the ML would be far more interesting if this wasn't a second chance type of story. if we had stayed on the original timeline, this story would be so dark and fascinating. don't get me wrong, i like it anyway but making this a realistic manhwa with no going back in time would've given it so much flavour. i wish we could see more of timeline 1's ivorre!