I was looking at Delphi: array of Char and TCharArray "Incompatible Types" and started experimenting. What I discovered is rather interesting.
proc
Since the documentation specifically mentions open array parameters of type Char to be compatible with dynamic arrays, this should be a bug. From 'Open Array Parameters':
function Find(A: array of Char):
Integer;
[...]
Note: [...] The previous example creates a function that takes any array of Char elements, including (but not limited to) dynamic arrays. [...]