1) Sorry about that, read your question too fast. Was just reviewing the Fagor website and this company is based in Spain which uses different European wiring standards than the United States does.
2) Fagor's electrical installation instructions show that the oven green/yellow wire is connected to both the house white (neutral) and green/copper ground wire. A green/yellow wire is only meant to be used as an equipment grounding conductor and not combined with a neutral conductor. I disagree using that type of wiring scheme for an oven installed in the United States. In the United States, the white neutral wire is also a current carrying conductor and is used as the return wire going back to the electrical utility transformer. This oven is a 240 volt supply which also has a clock as well as other various controls which require to be powered by 120 volts and not just 240 volts. The 240VAC is only for the oven. The 120 VAC portion is for the rest of the controls, clock, etc.
In the United States, any 120 volt AC circuit has 1 hot and 1 neutral and an equipment ground either via a bare copper in Romex or EMT metal conduit. If the neutral wire is connected to the ground wire, this defeats the purpose of the ground wire. A ground wire is installed for safety purposes and should never have voltage and/or current on it unless there is a ground fault which would immediately direct it to the path with the least amount of resistance which is always the ground or earth.
If Fagor is internally bonding the green/yellow ground wire to the frame of the oven and it is tied into the house neutral wire, this means that any return current on the 120 volt portion is going thru the frame and metal enclosure of the oven.
3) Any electric double oven or electric range that I have installed over the years was either a 3 wire circuit (2 hots & 1 neutral) or a 4 wire circuit (2 hots, 1 neutral and 1 ground) such as your house. Prior to 1996, the National Electrical Code allowed 2 hots and 1 neutral and did not require a separate equipment ground.
4) I would suggest contacting Fagor and ask them if this particular model is only meant to be installed using European wiring standards since it does not meet our wiring standards here in the United States.