Maintainability. Think about having a list. You add constraints between all the rows etc. then remove a row in the middle. Now you have to update all the constraints
i think that in cassowary that involves removing roughly one constraint for each thing on the row, then adding a new constraint for the newly adjacent rows? then because it uses an incremental solver it can reuse the part of the previous solution for the rows above the deleted row, just recomputing the positions of the rows below
but that's a question of performance. 'maintainability' would be removing the code that adds the row to the list, which is trivial with cassowary