Cross-cut then extend
The proverb cross-cut then extend (or the first to extend from a crosscut has the advantage) is somewhat misleading. There has been a lot of criticism that can be read at the /Technical Discussion page. A way to interpret the proverb is to reduce it to a not so common situation:
- When there are no other stones nearby, extending from the crosscut gives the advantage
Some diagrams to explain.
It is tempting to play atari. Then connecting at is a good idea. However, this strengthens White and weakens the lone Black stone. A ladder at a may be possible.
After the more defensive-looking extension it is White's turn.
However, White has to make a choice of which stone to strengthen. This is in fact an application of the 1-2-3 principle: if you are going to strengthen at in the previous diagram, why not do it at once as in this diagram.