Oh.
You mean IJ/IP/EJ/EP vs. SJ/SP/NT/NF? Yeah, I think the bookend letters are more valuable than Keirsey, because it tells you HOW they use their functions, rather than WHAT functions they use, which is easier to tell upon meeting someone. It's easier to figure out someone's basic "style" than what's behind it. In certain situations, an INFJ could look like an ISTJ, or an ESTP could look like an ENFP, etc... it goes on.
It's easier for me to see:
IJ - reserved, serious and focused
IP - quiet, a little impulsive, but open
EJ - strong presence, somewhat open, focused
EP - somewhat haphazard and goofy, rather expressive and absorbed in their surroundings, very open
I see these all the time. I never see SJ/SP/NF/NT in other people unless I get to know them really well, and sometimes not even then. That's been my experience.
Most of the SPs disagree with me, but maybe it's because they get vibes I don't get from people, and I get vibes they don't.