The deform parameter of the Bmesh from_object method is deprecated, always assumed to be True, and will be removed in version 3.0. That is because the cases where it is False don't work correctly and are subject to memory leaks. One of the symptoms of the incorrect behavior is the application of constructive modifiers twice if the input object is an evaluated one, as demonstrated in D10053. Reviewed By: Brecht Differential Revision: https://developer.blender.org/D10086