Yeah, I had the same thought. However, the Switch actually makes that convenient, by design. I would play my PSP on TV all the time. It sucked. Getting the screen full size required your TV to have that option (and crappy cheap TVs didn't). Fumbling with the wires was annoying. It didnt have a stand.

The Switch has the same feature, you're right. But its designed (and marketed) around it. That's the difference.

Too small because of underscan? I'm baffled why with HDMI and the 1080p standard it's now the other way round - I need to disable overscan to get the full image and games still have to prompt me to choose a safe area to display UI elements.

You can play the PSP in your handheld and connected your TV.

With the Switch you can use it docked, handheld, and tabletop (i.e. stand alone).

Speaking of docking, there was this phone + tablet hybrid from Asus: https://www.asus.com/us/Phone/ASUS_PadFone_X_US/gallery/