[mictester]

When I was trained, it was called "offset tuning" and was a method to slightly broaden the selectivity of an AM receiver in an effort to make the tuning less critical and to improve the audio frequency response somewhat - particularly as some of the European stations didn't bother much about bandwidth limiting their modulation! It was made clear to us that it was a compromise, and that peaking the IFTs at the centre IF frequency would enhance sensitivity and selectivity at the expense of easy tuning and narrowed audio....

In the case of FM receiver strips, some models required offset tuning of the IFTs to get the requisite bandwidth to give the discriminator enough to demodulate!