The strut does act as the upper pivot point for the steering. I imagine it is possible for it to wear to such an extent that there is slop between the piston and the case.

Try jacking it up under that control arm, grasp the wheel at Noon and 6:00, and rock it to check for play. Perhaps something is worn or maladjusted the such an extent that your camber is way off, allowing tire to contact fender lip.

There is a bump stop on the strut that should normally prevent contact even if the strut bottoms. I suppose this could be damaged or missing.

Also, if you have oversize wheel or tires the clearance could be even tighter.

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1986 300E 5-Speed 240k mi.