The pinebook is a laptop with a 14" screen, this is aiming to be far more portable with a 4.5" screen (can we even get phones that size anymore?), so they're not really in the same category. It's competitors are more like the GPD pocket (https://www.gpd.hk/gpdpocket2) which I've been umming and ahhing over getting for a while as a machine I can do some coding on while commuting or laying in bed.

The silicon keyboard probably allows it to be smaller without fat fingers becoming an issue and this looks like a better form factor for my usage than the clam shell of the gdp. My big issue would be whether or not it allows for multiple keys to be pressed at once.

I agree about the silicone keyboard.

I can understand many mechanical keys types will not be feasible in a small form factor. But there are good mechanical key designs that are small to choose from. For example, the ones on HP calculators (ie HP48GX...) The DM42 (a modern HP42S clone) has nice mechanical keys.

https://www.swissmicros.com/dm42.php