Heheh ... fire at will then?
All servo arms work on the same principle...
They are basically pivoted arms with a moving pivot point.
So they have some of the same issues that any pivoted arm has, in addition to the advantages of an LT (and the difficulties of an LT).
Regardless of the brand/model etc, they all allow the arm to move on its pivot point, and detect the offcentre position, then shift the pivot to reposition things.
So yes, all these arms go out of tangent one way, get adjusted to a little out of tangent the other way, track across the zero point and the cycle starts again.
Depending on the design, many of these arms do not in fact "stop" the motion just accelerate and deccelerate it as needed, others do in fact stop/start.
The quality of the arm can often be determined by how well this adjustment is made - a tonearm is a VERY VERY sensitive device - some LT's have earned a bad name for audible "crabbing" across the record surface - ie: the motor turns on and shifts the arm, then turns off and the process is audible on the output (NASTY!). But this issue is no more or less common than bad bearings on a pivoted arm (regardless of whether the bad bearings are due to bad/cheap design or wear and tear).
Additionally there are the same differences on LT's as with any pivoted arms - there are unipivots and traditional bearings, static balanced and dynamic, damped and undamped, not to mention low mass and high mass, and even ultra short (gantry is over the record, sometimes in the TT lid) or full length.
In terms of the actual level of tracking error generated when the arm is at its max non-tangent point before being adjusted... any decent LT will keep this at substantially less than half the maximum error that any pivoted arm reaches.
An LT spends most of its time as it moves across the surface of the record at far less tracking error than any pivoted arm.
Even a 12" arm will have maximum tracking THD of circa 0.6% at its max tracking error of around 1%
With a Linear tracker like my Revox, the max tracking error spec is 0.5 degrees, on my own hand adjusted example, I've measured max error at 0.3degrees.
So your worst case Lateral Tracking Error (LTE) on the revox is around 1/3rd that of a 12" arm or 0.3deg vs circa 16deg - that means in THD terms less than 0.05% vs 0.6%.
Audibility and perception are of course a completely seperate issue...
But normally 0.5% THD is considered well within the audible range.
bye for now