I have a basic flow using the 'When an item or file is Modified' in SharePoint
All it does is updates a column with the word True, if the column is not already True, when the item is edited. It should only affect the record that is being edited but it updates the entire list.
Here is the list

Here is the flow

Here is the only field being updated

And here is the resulting list

It fills the whole 'Currently Assigned' column with trues, strangely enough it seems to miss one out for some reason; it wasn't the one I was editing.
Is this a bug or am I doing something wrong?