In short
account image is 'JPEGPhoto' attribute of user record and get the properties of the current user is returning 'Picture' attribute of user record.
Mac OS X 10.5+ stores user's account pictures within the Directory Service. User account contains a 'Picture'(that is a path to the account pictures) and 'JPEGPhoto' attribute in their user record .This can be read using the dscl command (dscl . -read /Users/username Picture and dscl . -read /Users/username JPEGPhoto | tail -1 | xxd -r -p > /accountImage.jpg).(initially both are same)
If a user has modified their user picture at any time using system preferences the account picture is stored in the 'JPEGPhoto' attribute of their user record not in 'Picture' attribute.
If a user has modified their user picture at any time using applescript the account picture is stored in the 'Picture' attribute of their user record not in 'JPEGPhoto' attribute.
tell application "System Events"
set the picture path of current user to "/Library/User Pictures/Flowers/Dahlia.tif"
end tell
Your applescript is returning 'Picture' attribute of user record.
Reference:
Where does the Mac store account pictures?