Hello Michael,
The module_init call is defined as device_initcall, which is one of kernel inicalls.
All initcalls are put to initcall section and kernel calls all initcalls at boot time.
You can check this in your vmlinux:
ffffffff81765ed8 T __initcall_start
ffffffff81765ed8 T __setup_end
ffffffff81765ee0 t __initcall_trace_init_flags_sys_exitearly
ffffffff81765ee8 t __initcall_trace_init_flags_sys_enterearly
ffffffff81765ef0 t __initcall_init_hw_perf_eventsearly
ffffffff81765ef8 t __initcall_register_trigger_all_cpu_backtraceearly
ffffffff81765f00 t __initcall_spawn_ksoftirqdearly
ffffffff81765f08 t __initcall_init_workqueuesearly
ffffffff81765f10 t __initcall_check_cpu_stall_initearly
ffffffff81765f18 t __initcall_migration_initearly
...