The "what" is exactly my point. One would assume dishwashers are supposed to do this for you, but what actually happens is the plate comes out with the (yes, small) bits of food hard and stuck to the plate (someone else mentioned "caked on cheese" in this thread).

I've tested this effect in multiple dishwashers at this point, always wanting the technology that was promised, but always in vain.

This is advised against in modern dishwasher manuals. I personally never remove food for mine unless it's been caked on due to over-cooking in a pan or something (obviously I scrape large parts into the bin, but I don't pre-rinse). And in most cases I'll often run it through first anyway to soften it up then scrub the remainder off afterwards instead since that results in less work.

In rare cases, food will be stuck to some items but this is usually due to geometry (something was blocking something). It's sanitised from the heat anyway so I just wipe it off and put it away.

I think the hard water residue can be solved with an additive, but it's not a problem in my area.

Strange, I only ever saw this happen on 20 year old dishwashers. Every modern dishwasher I have used, so long as your have correct plumbing and use a solid detergent requires no pre-washing.

I put my dishes in caked in pasta and sauce and large food bits. The only things that don't go in are anything that would disrupt a disposal unit. No bones, no stringy things like tomato vines etc.

Maybe the water hardness is set incorrectly or the salt hasn't been added? A dishwasher doesn't need pre rinsing.