It’s probably necessary, considering how the geometry you created looks. Search in forum for ‘tiny edges’ to understand why errors occur when you have very small edges.
I recreated the model to have a clean geometry and used a simple railing as an example, so there were no problems with Flowify. However, the railing you intend to create already has a lot of small edges, so besides there being a lot of them and it taking a long time to calculate them, once bent they will generate even smaller ones, hence the error.