Chansen, you are right, but it depends on the model and the mfgr.
In BC, and probably some other jurisdictions, the fine print must state what your true rate is. So if there is a rebate in lieu of the subvented rate, they must publish what the blended rate is.
For example The Sonata: If you were to finance $27k at 0%, your cost of borrowing is $3000 (the rebate you forfeit for the rate). Your true rate is about 4.7%. This is still good, almost a point below prime right now, and about 3 points below a bank fixed rate loan, and still will save about $2k over the 60 months vs regular finance.
If you financed only over 36 mo, true rate is about a wash with the banks, about 7.8%.