It's not just the physics stuff, which is necessarily watered down ( I found an article on a "simple method" to determine mean temperature based on latitude and... well, 12 pages, read it four times and said 'Nope'. )
There's also the PGL part of the UWP. The original book has pages of culture tables that if you boil it down are no better than the D66 that already exists in the Core book, so I saw no need to redo that, but on the other hand, Government and Law Level stuff seemed underdeveloped or at least under-explained in the old DGP book. And to the Traveller, details like, "Am I going to get arrested for that?" are likely more impactful than sky colour (which, even more fun with that: the Earth's sky is actually a combination of violet and white, but our eyes doesn't see violet very well, so it looks blue. Birds, whose vision extends into the ultraviolet, probably see it very differently. I can guess how Vargr eyes work, if they're not 'improved' along with their brains, but don't know how Aslan eyes work, and Droyne? - so the colour of the sky depends on the eye of the beholder {small 'b'} ).
So my point, which wandered off the page... is that there's much more to world-building than the weather. Understanding the society is just as or more impactful than the physical aspects. In Traveller at least, gravity can be controlled, so if you're strolling through the starport, you can be on any technological planet, but the wall decorations, security checkpoints, hawkers of goods, pickpockets, that is more likely to show the character of the world. I just finished reading Bu and Embla's Guide to Starports of the Marches (part of the JTAS Kickstarter) which gets that idea across rather well.