Re: To think Apple once marketed the Mini as a server machine (do they still do that)?
They don't market it as a server now but why would that need upgradable RAM, when you can spec it up with the most RAM it can support? That's a cost issue, not a spec issue.
More importantly, which the article didn't obviously mention(?) is that you cannot buy a quad-core Mini any more. That really hurts for use as a serious desktop or server. My guess is Apple realised the Mini is predominantly used as a media server or basic desktop and doesn't need those things.
Personally, I immediately bought the cheapest quad-core 2012 Mini from my local store while I still could - I was waiting for a refresh to buy a Mini for fear of buying an older spec, but it turned out the opposite. If I'd known in advance, I might've bought up a load of them and sold them on for a tidy profit!