Granting that they're different types of projects, but....How do we get from Yongsan Raemian to this?
^^Interesting question... to which I have no good answer.
Overall, Samsung C&T has struggled recently, and have been fairly inactive on the bidding market for reconstruction (GS, Hyundai or Lotte are at the forefront) so I don't think the group views apartment construction as a critical vector of growth, the same way it did a few years ago. Raemian is still a leading brand for consumers, but it could change a few years down the road as new project get completed from competitors.
Also, the project is perfectly located for investment value (heart of Gangnam), but it's precise location is not one which calls for landmark. It's a non-distinct apartment block, a bit far away from major avenues (Hyoryeong-ro is big, but fairly residential), subways, or businesses. So having a very expensive landmark here would make less sense I suppose. Developers probably look for high-visibility blocks when offering more aesthetically pleasing design (near the Han River, in front of a major rail station, at a busy intersection...). That's a trend which is not exclusive to Samsung C&T.
Finally, and that's the bigger reason, I think this has to do with the overall redevelopment philosophy and the city code as well. This development is one of many reconstruction projects in Seoul (and Korea), it just happens to be very well located. So the design is non-distinct. For Yongsan, the whole area in front of the station was kind of a slum before, and the decision was made to completely redevelop the area, building from scratch, redesigning the station, combining commercial and residential buildings, with offices in the vicinity as well (LS, LGU+, AmorePacific). And in the long run, combining the area with the Yongsan IBD project and the Yongsan Park (former US base site). So I guess there were some requirements from the city to have mixed-use project at Yongsan, so that usually means a good design with some cladding.
We'll see... it will be interesting to see if Samsung C&T reconsiders its positioning on the market, as some competitors have upped their game recently (mostly thinking about GS, Hyundai, Lotte and Daelim).
Finally, this render is the pre-sale render, and apartments will officially be put on sale in June, so at that time maybe the renders will have changed a bit, although I doubt it.