An opkg installs a kernel module, then postinst calls "depmod -a".  The opkg intercept causes the depmod invocation to be deferred until later.  Meanwhile, whether in this postinst or in a later one, attempts to load/use that kernel module fail because depmod hasn't run yet.

Hypothetically, the same issue could occur with the ldconfig intercept.  For example, if a package installs a library, then a later package wants to start a service that depends on that library.  The service start request will occur immediately, meanwhile the ldconfig call won't happen until much later.