Can you upgrade the RAM in the latest MacBook Airs if you ship them to Apple themselves? I know that RAM is soldered onto the mainboard on the latest MacBook Airs, which makes a DIY upgrade apparently impossible. But would Apple do it instead though?

The guy at the Apple Store told me that I could send the Mac back to Apple and they could upgrade the RAM, but he didn’t look very convinced if I must be honest, so I wanted to double check here.
Apple will replace the motherboard. The RAM is not desoldered and replaced, but the motherboard is simply swapped for one with the amount of RAM you want.