Yes, but those cars on that test run were empty.
No passengers, no luggage, no water.
Indeed, that changes things a bit, plus it was 8 cars. Weren’t there something like 16 or more connected to the train that crashed?
Regardless, after a point it doesn’t appear to change overall acceleration that much since it reportedly took about a minute to go from 80 to 106 in the case of this train crash incident.