ParticleSystem::clear_to_initial() does not reset system age

while testing Particle Systems, i found that if a ParticleSystem is set to grow older (set_system_grows_older_flag(true)) then calling:

particle_sys->clear_to_initial();

system age will not reset, it will retain it’s value (system age is NOT system lifespan). so for example:
1- the system reached the end of it’s age
2- clear_to_initial() is called
3- the system is added again to the ParticleSystemManager
4- do_particles(ClockObject::get_global_clock()->get_dt())
5- the particle system won’t run since it’s age has not been reset.
6- to reset age call: set_system_age(0)

is this by design? or a bug?