New, unexperienced people just being under the huge pressure all the time, during the tournament, because of people around them taking this as something more than simple GFs, that's why they can side block or something, but it's definitely not showing their real groupfighting skill. As I said before, it only shows their unexperiencedness.
Nowadays every member of TBE, Poosy, Snappers, many players of other GF teams don't feel the pressure anymore, tournaments are going on almost every Sunday, if you are doing it that oftenly you should be used to it, of course. That's why they are getting in some way an advantage during tourneys.
The best way to see groupfighting skill is still the league and practice matches, imo.
You totally misunderstood me, you can't rule out down to experience and inexperience, if you can't deal with high pressure group fighting matches such as tournament finals, if you don't understand the vastly different plays that are made in tournaments and the fact that almost all players are far more passive then in any normal GF then you can't be rated highly soley based on practice/normal GF matches espically when the opponents are often trash tier players or poosy who are trolling.