This decision has been taken following suggestions by some riders in the Safety Commission, where discussions over excessive race lengths had been taking place.
Nine Moto2 races and seven Moto3 races will also be reduced in length in order to make scheduling easier for race organisers.
On the MotoGP side, the seven rounds losing laps will be Austin, Jerez, Le Mans, Barcelona, Brno, Misano and Valencia. Most will be reduced by just one lap, although Jerez will lose two and Valencia three.
This reorganisation takes place a year before the arrival of the FIM Moto-e World Cup for electric bikes. Its calendar will include between four and six rounds, all of them in Europe.
The new championship will make Sunday event schedules even more packed as it is expected that these races (most of which will be eight laps) will take place before the start of MotoGP at 1400 local time.
MotoGP race length changes
Source : https://asia.eurosport.com/moto/motogp-to-shorten-some-race-lengths_sto6510280/story.shtml