AFAIK the Escom 1200 floppy drives were missing the _RDY signal, so the board had to be modified to suit. If you use an Escom floppy drive on an earlier board I would think that some game bootloaders and maybe xcopy might not work properly.
From reading around the last of the 1.d4 s were sold to escom which they modified to work with pc drives and the 2b is a fully escom revision.
The 2B can be modified to work with standard amiga floppy drives though.
http://www.softpres.org/article:hard..._fdd_connector