Since 248f59e5 (Business Template: Likewise ERP5Site.addERP5Tool(), do not re-create Tool if it already exists., 2020-06-22) we no longer update tools, because of the problem that business template does not currently handle updating objects with lots of sub-objects.
But we realized that we really need to update tools when they contain configuration as object attributes, like mimetypes_registry, where the problem was observed.
Instead of unconditionnally skipping any tool during update, we only skip the ones that were initially managed by ERP5Generator and are moved to business templates.