Generic IAX2 Device exten missing on 2.2.3

hi there

I am on freepbx 2.2.3 on Debian etch, asterisk 1.2.20

I created a simple IAX2 device to call iaxmodem, configured my iaxmodem, hylafax, etc.

that means I pressed on Setup - Devices - chose [Generic IAX2 Device] and chose the basic configuration described in this video

Once I tried to call the extension, I got a busy tone, and aboslutelly no activity i CLI, I am rather new to freePBX so am also trying to understand how it actually works and just out of curiosity, I added this line to extensions_custom.conf:

exten => 201,1,dial(IAX2/201)

and to my surprise, it works perfectly! well, with this I do get an answer from hylafax, so, isnt this supposed to be a basic part of setting up an IAX2 device? if it is not a bug, I would very much like to know how can I add the extension in GUI instead of using more files.