Op amp output DC operating point variation with load current
Fully BIPOLAR opamps may have gain reduction as Iload increases, what with operating point variation as finite-beta reflects Iload back into HighZ nodes.
This would be similar to a change in Early voltage.

Fully CMOS opamps, with the load merely changing the Vout as the FETs' triode-region alters with a true ohmic delta_Volts = Rtriode * delta_Iout,
are exhibiting a voltage_divider effect which is not a genuine drop in forward voltage gain.