The advantages seem numerous:
- many defenders are used to dumps catching the disc behind the thrower
- catching the disc up the line puts you in the power position (ie you have a 1 second window where you can throw anywhere upfield, including long, since your defender is behind you)
- it is a simple way to score when you are close to the endzone
- other defenders are often not in a position to provide help defence
- it opens up the backwards dump, once cutting up-the-line is an established threat
I realised that this is generally true only if you go far enough up the line.
So clearly we need a name for this.
When the dump has cut forward far enough that the thrower can throw to them, the defender has to commit to defending up the line.
Basically, the dump needs to enter the up-the-line throwing lane. I shall call this the Wedge (coloured orange in the diagram). It looks wedge-shaped.
To summarise: to open up your dump, Enter the Wedge first. Very Zen.