I have been exposed over many years to how a Cart' can be perceived in use, when exposed to the conditions being referred to. Unwanted conditions that can be avoidable or much much improved.
Many years past, on a heavily modified Idler Drive TT, a friend introduced a cheap MM to a SME 3009 Tonearm and had visitors assess the Pairing. The intention was to revisit over time, allowing for the Cart' to settle. The Tonearm was to undergo methods to improve its condition, i.e, Servicing and then adding upgrades, from mechanical through to Signal Wire. All revisits as the TA works progressed were assessed using the same MM Cart'. There was a point in time that the Cart' was clearly better than any recollections had, and the perception was it would be hard to better with any Tonearm Cart' configuration. The mind can play games, as a swap out to a different Tonearm and Cart' both known to be better choices, made the SME 3009 > MM sound very very poor.
I know through my experiences had, that when a Cart' is used on a set up that has attempts made to address the optimisation of Mechanical Interfaces and methods are in use that are able to support and effectively isolate the Critical Parts from excessive influence of Kinetic Energy Transferral, there is easy to detect changes to the sonic being produced as the outcome, the voicing of the Cart' being used can be very easily distinguished.
My experiences around a Certain Cart' Brand, when Cart's are being used between Certain Purchase Values from the same Brands Range of Models, or as a same range of model Cart' having undergone Modification, such a different Styli as a replacement only, or a Cart having undergone further modification. The differences from Cart's in use are quite discernable, when such Cart's Families are experienced in use on a system addressing referred to interface issues already mentioned.
I avoided the subject of off set Spindle > Groove centring LP's, as there is always a risk of this condition being present, when known the Vinyl Manufacture Quality Tolerance, where the Spindle Hole Centre is acceptable to be offset to the Groove by approx' 0.2mm.
The following will suggest why a 0.2mm off set can be classed as not too concerning issue, and the last one needing to be addressed, as it does not really contribute detrimentally to the energy being sent by the Styli.
I think on this matter the Industry, if able to maintain the standard for a tolerance of 0,2mm, has been fair to the Customer. Much Much more expensive items are produced to assist with extracting recorded data from the LP that are being sold with conditions much more detrimental to the quality of the sound to be produced.
Most record pressing standards have a production tolerances that are producing a centre hole to groove eccentricity tolerance of 0.2 mm maximum.
Apply the 0.2mm to a playback radius of 100 mm (approximately the centre of the LP modulated groove area) equates to a wow of +/- 0.2 % peak ( 0.14 % RMS). As this is for most an people inaudible, it does seem like a fair tolerance for a standard production item. Does a Premium production Item address the off-set to a Zero mm dimension?
Usually, when I refer to eccentricity of a rotation, I refer to the eccentric rotation of the LP, in conjunction, with the eccentric rotation of the Platter Spindle Bearing being the main concern.
Where the combined LP/Spindle Off Set eccentricity does become a little more interesting, is when there are individuals reporting that eccentricity is identified up to 5mm as the guestimated off set. Such reports about the off set being more than 0.2mm are quite incorrect, when coming from reports that are claiming noticeable movement of the Headshell that far exceeds 0,2mm.
Using the Headshell as the indicator of the LP's off set dimension, is only showing the effect of the force being applied to the Headshell as it passes the groove location of where there is maximum force being exerted, which is then incorrectly described as the full force being generated by the groove off set.
There are a Huge amount of variables as to why a reported off set from a visual observation can be seen to be approaching up to 5mm. As a layman, I would suggest the LP's 0.2mm off set is a very small influence on what is being detected and there are other influences contributing in a much larger measure.
How many individuals who are willing to report on a Cart's qualities are using a Cart' on a Tonearm that has a noticeable deflection to the Headshell, at a particular area on the LP's surface, that can be seen to be guestimated between 2-5mm as the off set deflection. Does different Cart's on the exact same set up with the LP placed at the exact same orientation on the platter produce identical off set deflection seen on the Headshell?
If this type of deflection was made known when one is supplying their report on the impression a Cart' has made, how much would another attach themselves to the report declaring it to be creditable.
Once more, where is the 'all things being equal', all thing are uniquely bespoke to each individuals experiences had at the replay environment.