It may seem like a matter of semantics, but there is a marked difference between the old conception of the forehand stroke vs. the modern one.
For one, there is more looseness in the grip, as less hand tension is necessary the more you adhere to laws of nature to produce your swing.
Modern tennis is more vertical, while conventional tennis is more linear, more horizontal. Modern tennis takes into deep consideration the gravity pull of earth on the ball, while conventional tennis theory largely disregards this fact.
The easiest way to achieve the newest result is to think “no-backswing” while you are running and tracking the ball, then, timed to what happens to the ball as a result of the bounce, just a small rotation of the upper body and hands back and forth to get momentum on the racquet, making sure you attack the ball from below so you get some topspin.
A smaller or larger “c” may result in the back part, naturally, but more like a complete “o” or circle by the time you hit the ball. If you include the finish and recovery it’s more like a figure 8 lying down.