I just noticed how the textures look in that screenshot of the trailer. They look pretty low res to me.
If trailer 1 was recorded on PC, then surely it wasn't on max settings? The trailer came out in 2011. I don't think they would've started work on the PS4 version by then. I mean...is there a possibility that trailer 1 was recorded on the PS4 and the promotional screenshots on PC?
More likely that they used the PC version but lowered the settings like textures quality, shaders, distant details, reflections, projected shadows, shadows quality and game resolution, those were possible to tweak in GTA IV. You could make the PC version look like the consoles version.
Although tweaking these settings any extra assets won't be removed like the trees, vegetation a light quality.
I don't believe that the house we so much talk about will be simple as in the LG, there is no reason for that and in the 1st trailer it seems that there were huge trees close by projecting shadows over it and the model was a lot more complex, so I don't believe that they had all that work which looked so great and decided to replace it by an empty house made of card box in a bald terrain. And the same applies to all the removed trees, it makes no sense.