Yes, that’s the short of it. Each pixel needs its own wires, readout, and processing chain, and resources are limited on the spacecraft. The cryostat (instrument that keeps the pixels cold) only has so much cooling capacity and all the wires add thermal load.

Future missions are planned with more pixels (Take a look at the EASA Athena mission and its X-IFU instrument), and to reach that goal they are using multiplexing methods to allow more pixels to run on fewer wires.

I couldn’t find any reference to that either.

Not needed, this is clearly a render, and not of any real device either. It’s a pastiche of retro elements in a nonfunctional, stylized arrangement. The “cassette” is a miniature rendering of full-sized reel-to-reel tape. The speakers are more mid-2000s era design language, and the colors are over-exaggerated for the era.

“I cannot find any official reference to this model”

That is because it is a fictional rendering.