from typing import Tuple, List
(x1, y1) = (1, 2)  # type: Tuple[str, int]  # E: Incompatible types in assignment (expression has type "int", variable has type "str")
[x2, y2] = (1, 2)  # type: Tuple[str, int]  # no error - bad
reveal_type(x2)  # E: Revealed type is 'builtins.int' - bad

Since the notation [x1, y1] is just another syntax for target list, the above notation should work. But even if they shouldn't, mypy should at least warn about mismatched notation.

IMHO mypy should not differentiate at all between the cases after parsing - there should be only TupleTypeTupleExpr for lvalues.