A thought about the planet in Alien Covenant

So when the Engineer sacrificed himself and it shows him falling into the water and his DNA (which is similar to our human DNA); then what was the purpose of that scene?  Why would the Engineer ship be flying away if it was their planet all along?  

I would think they would have small aircraft to drop the Engineer off on a remote location on their homeworld or at least leave behind more than one if they were going to populate that planet.

Don't get me wrong, I believe it makes a lot more sense that it was our Earth origins. 

However, to answer your question, it is not earth, just another seeded planet.

The purpose of the scene would be predicated on Ridley Scott knowing exactly what he was to do with Covenant, having there be a reason for why the engineer-like people looked different. The explanation being that it is another Earth-like experiment, hence the people looking kind of like them, kind of like us. You can call it Earth II, simply another place they seeded life, and occasionally returned to visit. 

I am not one to believe that it was planned so meticulously, even though my heart would prefer that, of course.

I read various websites and many theories suggest that it was earth; some say that is how the Engineers brought life to lifeless planets.  

Even though the Engineers is now part of the Alien universe, I was so disappointed by their explanation and their role in the series.  The initial idea to drift away from Alien then to come back to it; really ruined what could of been a great story of what the space jockey was.

I would have had the Space Jockey simply be a friendly alien race with no ties to humans that simply was A) the source of creation for the Aliens or B) stumbled upon the creatures and try to exploit them for whatever purpose that led to grave results.

I am with you, brother. I thought the Engineers could be a great standalone story that addressed wider issues, keeping the Alien mythos intact, allowing their true horror or being mysterious, to remain pure. I was fascinated by the philosophical stories that could arise, and felt after a few movies of that, it would be a welcome treat to come back to Alien, and the Xenomorphs (briefly)! 

However....

It is clear that negative reaction rather influenced Ridley/the studio/whomever, to abandon the arc, and I think that is the reason behind my post. A hopeful grab that it was a long-term plan all along, that is was not Earth, and that it was more than "lets go to the home planet, wait, no, we need to avoid that taboo arc". It is possible, all elements put together and disbelief suspended, that it was not Earth, however I fear it was, until Prometheus got negative reactions, and then just glossed over.

Hope and all that. Hope in something bigger. Just call me. Dr Shaw!