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.

It definitely was available. I had an 83 300SD with Tex.

I remember the 1990 S-Class brochure had samples of both leather and Tex. Everything up to the 420SEL was available with Tex. 560 came with full leather and heated rear seats as standard.

However, in speaking to the dealer in 1990 they said every car they ordered was leather. The 350SDL might have been an exception (they thought) as there were a few customers that wanted the cheapest diesel S class they could get, so a few of those may have come with Tex.