You're making things up as you go along. After throw in and bringing ball back to wing there were 7 Tigers and 5 Saints, not the other way around as you say. The try was a result of terrible defence tactics. 2 on 2 and a back versus a forward with that much space out wide was always going to end in heartache. This should have been an example of rubbish defence.
This is dummy runners. We were using them in RL in 80's. Who on earth is using the term screening? If one is actually screening then there is obstruction. Defender must be able to see the ball at all times. If ball is hidden behind one of your own players it must be obstruction. Once again NH rugby showing how inept they are at even the simplest of structures and Sarries move actually had the #12 through the gap, but as usual in NH rugby, they call a move and they have to do it no matter what. League has really developed the dummy runner structures so well, with very quick hands practically at the gain line. It is a wonder to watch. There is a very fine line between holding the defense and running into them causing obstruction.
Or at least find a good highlights vid. I'm in US and I couldn't find a feed on any of the aggregators. Hey, rugby fans, if you are moderately wealthy please learn how to rebroadcast your tv feed to an aggregator such as cricfree and vipleague. Then the whole world can watch.