I've done a dozen front brake jobs on an E53 and I've never noticed a difference in pads. The inboard pad clips into the piston and the outboard pad just floats in the carrier.

What sort of reference mark do they describe? The pad ears are identical on the backing plate of all four pads.

I wouldn't worry about it if I were you.

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12 E70 3.5i xDrive
03 E46 330i ZHP
01 E53 3.0i
98 E36 323is
12 Audi A4 Quattro
79 Triumph Spitfire
73 MGB