I do not agree with it at all!
System is behaving as it should. New dates are necessarily new lines. For the same date you will have the replacement behaviour.
If you set the update period to something larger, like month, the values will be replaced also inside the month line.
You could use an info structure without period, or using always the same period. The result would be in this cases what you expect, except you would lose the Reqd Del Date information.
This could be solved with some code in the info structure update rules.
regards,
Edgar