> Replace np.column_stack with np.vstack().T

If the AI is telling the truth that these have different performance, that seems like something that should be solved in numpy, not by replacing all uses of column_stack with vstack().T...

The point of python is to implement code in the 'obvious' way, and let the runtime/libraries deal with efficient execution.

Read the linked issue. The bot did not find anything interesting. The issue has the solution spelled out and is intended only as a first issue for new contributors.