The 'bug 'of the ADO dataset lookup fields in Delphi'

This is a letter I wrote to Borland, but they did not reply.

However, the content provides error causes and solutions.

Body of the email:

I am a loyal fan of Delphi.

I have never understood a problem. If the lookup type field in the ADO dataset control has a null value in the field pointed to by its lookupkeyfields attribute, 'eoleexception with message' an unknown error occurs. After debugging, it is verified that there are only three solutions:

1. Set the autocalcfield of the dataset where the lookup field is located to false.
2. assign a value to the lookupkeyfield when append of the dataset where the lookup field is located
3. Set the lookupcache Of The lookup field to true (the speed is greatly affected)

Should this be a Delphi bug? If it is a bug, why haven't delphi5 made any changes till now?
If it is not a bug, is that normal?
I hope your technical staff can answer this question. Thank you.

PS: Our company is a genuine user of Delphi. We hope Borland will become stronger and stronger.