The format was recently changed, in an effort to meet Treasury Board and other guidelines to contain clear and concise language, etc. Tt has changed more than once in the last five to six years, as well.
I have a file on my desk right now, with four decisions in it, from May 2014 to July 2015. Three of the decisions (all in 2015) are preceded by a cover letter, containing a basic explanation of the decision itself. There is no signature block on the cover letter. Attached to each of the three cover letters are the decisions themselves (Departmental Review, Assessment Decision, and Official Decision). Each of the actual decisions has a signature block at the end. Neither is on a separate page from the remainder of the text of the decision, and each page is numbered at the top.
The other Assessment Decision, from May 2014, has no cover letter, but it does have a signature block at the end of the letter. It is not on a separate page; rather, it flows "naturally" from the main body of the letter.
If the 2004 and 2007 letters were both signed by the same person, I wouldn't find it surprising if it changed over the three-year span...specially if they are signing more than one letter a day, as the Adjudicators would be...
It's like signing rent cheques for the year...not going to be the same from cheque #001 to #012.