I've a theory about what this is doing:
As the wheels have an amount of negative camber, it means they're trying to turn in to each other (imagine they're part of a cone). The toe-out, sort of, corrects this.
The camber and toe cause 'scrub'.
By reducing the toe-out in a straight line, the amount of 'scrub' is reduced, hence reducing friction, giving a , marginal, increase in performance.
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