I think this is a correct behavior.
$ cat -n multiline_assignment.py
1 x = 1
2 y = 2
3 z = [
4 x,
5 y,
6 ]
$ ./python -m trace --trace multiline_assignment.py
In 3.7 the line with the assignment is missed:
--- modulename: multiline_assignment, funcname: <module>
multiline_assignment.py(1): x = 1
multiline_assignment.py(2): y = 2
multiline_assignment.py(4): x,
multiline_assignment.py(5): y,
In 3.8:
--- modulename: multiline_assignment, funcname: <module>
multiline_assignment.py(1): x = 1
multiline_assignment.py(2): y = 2
multiline_assignment.py(4): x,
multiline_assignment.py(5): y,
multiline_assignment.py(3): z = [