That sounds a bit strange because the pump basal is delivered several times per hour. I can hear my partners pump do that because of a clicking sound. I dont think that people on mdi have more spare insulin than pump users, on the contrary I think pump users have an advantage because of the steady release of insulin throughout the day that more mimics the pancreas release of insulin.
I guess it is very different from individual to individual. If you need to bolus for a few carbs you will notice but I dont think it has anything to do whether you are on a pump or mdi.
This is how it was explained to me ...
A basal bolus injection regime assumes your basal requirements are the same for 24 hours a day and we take long acting insulin to last this period.
As we are not moving much at night, typically, our basal needs are higher at night so, during the day, we have basal insulin which may not be being used by the constant liver drip.
As you say, the long last insulin does not mimic a healthy pancreas.
If we do not eat, exercise, get stressed, we may find our BG dropping during the day although we remain stale throughout the night.
This is what I mean by spare insulin.
In contrast, with a pump, we can adjust our basal to match our body's actual need at different times of the day. Therefore, if we didn't eat, exercise, get stressed, etc. our BG should stay stable at all times.
As you say, each of us are different and a few carbs will affect each of us differently.
If it works for your partner the way he manages his insulin today (you would best see on a CGM or Libre), there is no need for him to change anything.