Why does record shape not support flat edge?

As the title shows, why can’t two nodes be at the same level when one of the nodes in the flat edge is a record?
I try to run the following dot and get the following prompt:

Warning: flat edge between adjacent nodes one of which has a record shape - replace records with HTML-like labels
  Edge a -> e
Error: lost a e edge

dot script:

digraph G {

Here are two comments from the original developers that start to discuss “why”:

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