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The track of the Spitfire was ~6" less than that of the Bf109.
If one tire or the other gets significantly more pressure (or weight on it) than the other, as in a crosswind where one wing lifts a bit, then the main gear will move in the direction of the wheel with the greater weight on it. If the pilot isn't very quick with the rudder or brake or both, a groundloop can easily result.
Fitting a tailwheel lock helped but did not eliminate the problem.
I've never understood why Willy didn't toe-in the wheels so they were parallel in the 3-point attitude and toed-in during a wheel landing.
It would have corrected the worst of the faults and was almost ridiculously simple to accomplish. Then the swings on landing and takeoffs would have disappeared. Further, I'm surprised no crew chief came up with field mod to handle it.
It may well have been a case of simple pride that they didn't need a "fix" to handle this fighter, I can't say and would not care to speculate.
An aviation expert (??) by the name of Crumpp has stated that 'toe out' is better than 'toe in'.
I'm not convinced that visibility was such an issue.
I've been trained to use a combination of a point in the clouds, and peripheral vision to judge swing.
Maybe you should go back and read what some of those reports say. Experienced pilots could handle the Bf 109 with relative ease but it is the less experienced pilots flying an unforgiving aircraft that were the problem. I can't quote every reference to this but Antti Tani sums it up nicely in the link you gave.