No, they could not do that. Otherwise that'd be exactly what would have happened. Every one of those things is a major engineering change, and so engineering constraints have to be the topic of what you're asking for, not superficial spec sheet items.
The Note 9 did that over the Note 8 by getting bigger and changing the internal configuration of components, etc. The Note 9 has 1.8% more surface area and 4.1% more volume.
But Mario - I'm ok with a slightly bigger phone if it has better specs! If Samsung can do it, why can't Google? Well - I'm glad you asked. It's because, as we've talked about dozens of times in this thread and others, Samsung is a Hardware company, and is among the best in the world at Hardware engineering and innovation. Google, on the other hand, is a Software company and is basically using what it sees in the devices made the year prior to keep up as best it can. There's almost zero hardware innovation happening in smartphone design on the Google front. But didn't Google buy HTC's engineers? Yep, they did. But that was too recent to have any positive impact on the Pixel 3 or Pixel 3 XL, both of which are merely enhancements of the Pixel 2 and Pixel 2 XL existing designs.