Absolutely not! Please stop watching SLOP youtube videos and then claiming it's true. Think about this and use your brain. As a journalist, this is your responsibility. You aren't there just to copy and paste BS. The thing has 16gb of ram in small modules. It's not a large amount and won't matter. It will be like a 30 buck difference if that. Valve won't apple greed monger us.
DDR5 is cursed... it was too expensive when it first came out to attract people's interest, and now it's the same story again due to excessive speculation around general artificial intelligence, which certainly won't be born for several decades. Developing robots as we do now is one thing, but wanting to compete with the human brain is on a whole other level...
Since the Steam Machine's CPU-GPU combination (AMD Zen 4 CPU / AMD RDNA 3 GPU) is not the latest generation, they could perhaps use motherboards with DDR4 for the time being, at least until DDR5 prices come down.