I'm not completely sure about this particular transmission. But, many manual transmissions are ruined by towing in neutral. This is because the output shaft is turning, but there is not sufficient lubricant thrown onto the rear bearing and shaft.
It takes many more miles to ruin a manual transmission, but it will ruin it.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in