I think you should sue those b*st*rds, they stole you 4 ohms each.
They did never imagine you would actually *measure* them, did they?
Now I would ask not only for what they stole, but, say, an extra 4 ohms *each* for damages.
I forgot .... plus interest !!!
Now on to serious stuff: what you are measuring is the DC resistance of the voice coils; he actual speaker impedance will always higher than that, and varying with frequency; so to make life easier, a "conventional" value is used, some 20% to 30% higher t5han VC resistance, so those almosd 12 ohms indicate a real-world speaker of around 16 ohms.
The exact value is imprecise, or, better said, complex.