I do not believe the answer that you have received from LF Technical Support in Spain is correct. Watts are watts. There are not different kinds of watts. It’s possible that the measurements coming from the IC7 might be slightly less than the measurements coming from a set of power pedals or from a power crank arm because the power on the IC7 & IC8 is measured further “downstream” than those other two methods. But I don’t think that it would be such a significant difference. Also, keep in mind that the IC7 & IC8 have an extremely accurate power measurement system (±1%) that optically measures torsion at the spindle. Power pedals and crank arms have a more indirect power measurement method. I’m not familiar with all the different trainers that attach to the rear frame of the bike, but I would suppose that there are some that are equally as accurate as the IC7 & IC8 and there are others that are much less accurate depending on how they measure the power.
I have a 2018 IC7 that I have upgraded to TFT 2.0 console. I can maintain 250 watts steadily without issue and I am not a very powerful rider. I think that your machine may need calibration. Have you tried the “OFFSET” and “BRAKE CALIBRATION” procedures found in the settings menu?
Also, are you sure that your friends are not using virtual power?