Why "embedded file" instead of "linked" file ? Because it is easy to manage :
-you have only 1 file : the ipt. If you need to copy, move, rename,... the file, you don't have to know if there is another file to modify too. If you have a linked file, you cannot rename it or the ipt, if the folder is renamed the linked does not function any more, etc. With only 1 file it is much easier.
-each ipt file has its own parameters sheet. If you have a linked file you have to copy and rename the xls file for each ipt file. With an embedded file you don't have to manage this
-all needed information to use the ipt is in the ipt. No links managed by Windows.
-impossible to modify the xls file if you are not in the ipt file. The only person who can modify it is the Inventor user. If you have an external file, evrybody can modify it and so corrupt the ipt.