until really requires an event.
"he has eaten everything" definitely provides that event- the moment the last morsel is finished, junior may leave the table. The action is completed, and the consequences of that action are in Junior's stomach. It's the same as "he has posted the letter".
"he eats everything" is less satisfactory: it sounds more like a habitual action, which does not provide an event. Set against that, "his parents make him stay at the table" is a habitual action- they always make him do it- so the present simple as a habitual action is justifiable in that context.
Some verbs indicate events- throw, fall, die and swallow. Others like read, run, watch and eat are activities. An activity has a minimum of two events- a start and an end- it can also have a middle, but that's not so precise. When talking about past activities, we normally assume that the end is the event
I read this book yesterday (could be continuous, could mean finish)
for future activities, we normally assume that the start is the event
We will eat at 7pm. (future, start)
We eat at 7pm (planned or habitual, start)
We can indicate that we don't mean the normal event using start and finish
I started reading this book yesterday
We will finish eating at 7pm.
We usually finish eating at 7pm.
With until, we use present perfect simple to indicate future completion of activity verbs. Compare these two sentences:
I will stay up until I have read this book (PPS - sounds OK)
I will stay up until I read this book (present simple - sounds strange)
using PPS with event verbs in the positive definitely seems wrong:
We will shop until we have dropped
But in the negative, it can be used to imply doing something after the event
Don't open your present until I have gone.