Is a hold-down kit required for panels with a back-fed plug-in breaker as main?

According to NEC 408.36(D) Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are back-fed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.  "Field-installed" is the key, if we as the manufacturer use a back-fed breaker or main lug assembly in a panel a hold-down kit is not necessary.  If a customer back-feeds a plug-in breaker or main lug assembly that they field install a hold-down kit is required.