I also noticed  that when following the tutorial, and using a batch_size > 1 the loss converges very early, this potentially explains the results I am getting from my first question.
Is there a bug in the tutorial code?
Loss observed when varying batch_size in range [1, 2]

Here is a graph showing what happens to the loss when I move from a batch_size of 1 (with increasing max_sequence _lengths (purple:30, blue:50, orange:80, brown:100). Then increasing to a batch_size of 2, with increasing max_sequence _lengths(red: 30, green:50).