^Agreed. Say you serve to the deuce court and are coming in. They lob your partner. Player who strikes the lob stays back at the baseline (very common scenario at 3.5/4.0).
If I can catch up with that ball, I can hit a crosscourt volley into the huge gap between the deep player and net player. Deep player can try to run this down, but she will be hitting a running BH against two players at net.
As slewisoh says, the approach volley can also be taken up the line -- hard to do on the BH side but easy to do on the FH side.
When our pro first started teaching us to do this, we looked at him like he had two heads. It seemed impossible. Now I find it easier than bouncing the ball, getting into position and hitting a drive. Especially if the deep opponent followed the lob to net.
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-- Master Moonballer