It may have some validity since solar charges the battery every day, thus the battery may never get discharged below 60 or 70%.
There may be times that the RV is unplugged and the converter does not get to charge the battery until the battery is discharged further than it should be. That could shorten the battery life. That would be dependent on the RV owner's attention to detail.
If the converter charges the battery whenever the voltage drops below about 12.3v, everything should be the same as on solar.