I don't know what qualifies a sock to be able to be called a "compression sock".
To be a qualified MEDICAL grade compression garment, the compression has to have a compression rating in milimeters of mercury (mmHg). It's more compicated than I can explain here. The strength of the compression is meaured this way. Also, depending on what you want the compression for (bed or walking), you would need to know if the garment has graduated compression, meaning, varying degrees of compression to help facilitate lymphatic movement, etc..
A common misconception is that if a compression garment is difficulty to get on, you can just size up. That's incorrect. Compression has to be gaged to what you want the garment to do.
As I stated, Tommie Copper isn't claiming these socks are medical grade and can be used for edema, but taking calls and acting as if these are anything more than tight fitting socks can serious harm someone with edema. You can actually make the situation worse by trying to "help" edema with an ill fitting "compression" garment, sock or otherwise.