In fact many people do not know that proper loading is usually done from a selector switch on the phonostage in which the switch run through a series of resistors. Someone looking to have there preamp get the proper load for their cartridge is a very simple thing. Just look up the spec on the cartridge and insert the proper resistor in the phono input stage of the preamp.
@lowtubes If we are talking about an SUT in the signal chain this is just about guaranteed to not work. But if you enjoy the sound that's fine.
I ran an LP mastering operation and recording studio so I have LPs I recorded. My perspective is thus a bit different; using LPs you recorded make a great reference for really knowing what is going on.
If you weren't referring to an SUT in the quote above, the loading resistor is really for the benefit of the phono section rather than the cartridge. When the cartridge plays it generates RFI (Radio Frequency Interference) which might be as high as 5MHz on account of the inductance of the cartridge being in parallel with the capacitance of the tonearm cable. Some preamps react poorly to that RFI so their designers added a switch to allow you different resistors which detune the resonance that causes the RFI. But if your phono section doesn't care about the RFI its plug and play.
If you were talking about an SUT above, the capacitance of the tonearm cable and the cable between the SUT and preamp plays a role in the correct loading values (meaning its not something you can just 'look up'). Sometimes the correct load isn't just a resistor but a resistor and capacitor in series.