I get where you're coming from, and to a point I agree. However, the differences you're talking about are largely minor. Small shifts in tone or direction, maybe a few tweaks to history, and that's it. And it all flowed from issue to issue, year to year, without a clear break to set them apart from each other. Except for Birthright, which was never meant to be canon in the first place.
Superdad is a different matter. We're still dont know exactly what his history looked like and post-Crisis was a total mess by the end anyway, with at least four different origins in play that each brought vastly different approaches with them. How then are we supposed to judge Superdad's history, when the foundation he's supposedly built on is so fractured? The only thing Superdad has in common with post-Crisis is his wife. Everything else is different. He has as much in common with the Silver and Bronze Ages as he does post-Crisis. In fact the only era he doesnt seem to pull from heavily is the Golden Age, and even then there are subtle aspects that could be traced back to those early stories (such as his temper).
If his personality isn't strictly post-Crisis (insofar as that era had a singular personality ascribed to him), if his status quo is vastly different, if almost everything about his life is barely recognizable as a strictly post-Crisis construct, then why are we calling him the post-Crisis Superman? Because he married Lois? That's not enough in my book to call him the same guy. He doesnt feel like post-Crisis, his world doesnt look like post-Crisis, and if his history is the same it still doesnt change the fact that the stories in my hand right now feel like something new. The best we can say is that he's informed by the character's past. But that can be said of every version, even post-Crisis, which worked hard to distance itself from previous eras.