I think they are referring to those mini PCs -- either new ones from Chinese brands with Intel N100 or "refurbished thin clients" from HP or Dell -- that cost ~$150 but are way more powerful than a raspi in terms of performance and capability.
Comparing a refurbished PC to an SBC is like comparing apples to oranges.
I think the only people who are disappointed are the ones who were buying the wrong tool for the job.
You get a Linux SBC if you need some combination of small size, low power, convenient access to peripherals (I2C, SPI, and so on) or other unique features.
If you really only need the most powerful computer you can get for your budget and you don't care about the SBC features, you probably shouldn't have been buying Raspberry Pis to begin with.
And actually many raspberry pis are sitting around doing nothing, because people realize that they aren't interested in the embedded side of it, but the "computer" side of it is too weak to do anything useful. In that sense it is even worse than a mini PC which has enogh power to do some "real" light computer work.
And I didn't make any of this up. These are real things that I see people talk about, all the time.
There are lots of projects that need a small cheap computer that doesn't really need display.
It's still works but I sent mine back with an about 3 days since I couldn't do all the things I could do on a raspberry pi.