The backspace doesn't, necessarily, remove a character, it moves the "cusor" back one space. If you do something like this:
find . -name 'bleh*.*' -printf "%f\b\b\b\b\b\b\b \n"
You'll have what you want, visually. However, this just replaces the .123456 with
If you redirect the output to a file and vi, emacs, or pico it, you'll see what I mean.
To get what you want, you need to pipe the output to another command like cut or awk:
fine . -name 'bleh*.*' -printf "%f\n" | cut -d"." -f1