On 07/16/16, Darryl Perry said the following...
 
 DP>  g0> The execute dos program command creates DOOR.SYS, DORINFO1.DEF and
 DP>  g0> CHAIN.TXT in the node's temp directory.
 DP> 
 DP> You should mention that you eliminated the DC, and DG options, and now
 DP> have only DD and D3, because now they handle all the different options
 DP> between them.

He mentioned it a while ago when he replaced it. Running through the
WHATSNEW.TXT I can find where in v12a8 back in March he annotated as well:

 - Removed all door menu commands except for DD and D3.  The old ones will
   continue to work for now, but there are only 2 commands (DD and D3) to
   execute a DOS or Door32 door.  Mystic creates all drop files now for any
   door execution.

It's also in the Mystic wiki, you can browse by revision and version, and
also do a search for stuff if you want.

--- Mystic BBS v1.12 A28 (Windows)