https://www.44teeth.com/motogp-rear-rid ... explained/
But these rear ride height devices weren’t just helping the riders avoid wheelies during the race start. According to anyone that’s used them, they’re a big benefit during any ‘wheelie phase’, which is any time you’re accelerating hard in a low gear. That’s why you’ll often see the rear of a MotoGP bike squat very deliberately on corner exit. The rider simply presses a button and a mechanical or hydraulic system allows the rear to squat, lowing the centre of gravity. Any additional mechanical grip is also extremely welcome in racing. This means less electronic intervention and, ultimately, a faster lap time. That’s lovely.
It has to be manual because otherwise it would probably be considered as a rider aid and not many of them are allowed.
And here is a great view of Joan Mir using it at the exit of last corner in Austria
And here's an example from Qatar with Yamaha and Ducati when exiting the last corner