That is correct information. (Unfortunately it is true that cloth seats/door cards were unavailable in the American market).
Most Mercedes-Benz dealers in North America ordered the w126 cars fully optioned, and always with leather seats, (correctly) believing that most American w126 buyers did not believe a car was a true luxury car unless it had leather seats.
MB tex was NOT available on the w126 class cars at any point either in euro or US spec guise. Only on the (lesser) C and E class was it available.
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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...
1995 E 420, 170k "The Red Plum" (sold)
2015 BMW 535i xdrive awd
Stage 1 DINAN, 6k, <----364 hp
1967 Mercury Cougar, 49k
2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive

(sold)