As we see, there are many possibilities and variations on finishes.

If you set a minimun finish altitude on a finish cylinder, you can do the
same for the finish line. No difference there.

It is good to have the line/cylinder so that you can finish and land
directly. But if there are no trees etc. before the airfield, you still have
the low high energy finishes. They just open the airbrakes in high speed
just after the finishline and land straight. So it can still be quite
dangerous.
The finish line should be before the airfield and you should have there a
minumum altitude limit. Or ?

Soaring is not a spectator sport, but we all go out to see the finishes. But
there is not much to see, if the gliders come in slowly and land straight.
Okay, you still have some drama in it, if you know the start times so you
can see who has flown fastest.