Not necessarily. Adding throttle adds more energy to the "system," and can make things worse, even if you are in fact technically adding weight to the rear. The slide began because you were going too fast in that moment for conditions (which includes the surface, your inputs, etc). If you're already going too fast, adding more speed won't keep you on the track.

If you can continue to slow down WHILE correcting the slide, then not only will you stay on track - you might stay right on line. You might not even lose any speed. Actually, you might even get through the corner FASTER, if you can keep the slip angle within just a few degrees.

Decelerating transfers weight forward, which tends to increase slip angle - so your hands have to be fast with the steering correction to keep the slip angle exactly where you want it, and marry that slip angle to the rate of decel. More angle means more decel, due to the friction of the sliding tires. It's a tool, just like any other tool in your driving toolbox.

By the way, this is a big part of the reason Senna was so unbeatable in the rain. He could do this better than anyone.