Teams with 2 way players are allowed to let a pitcher rehab while letting them hit in the bigs. That team does lose the right to bring up someone to replace him. I'm kind of indifferent to it. It may help a team but not greatly.
https://www.mlbtraderumors.com/2020/01/new-rules-allows-angels-to-keep-ohtani-on-roster-as-hitter-while-on-rehab-assignment.html
https://www.mlbtraderumors.com/2020/01/new-rules-allows-angels-to-keep-ohtani-on-roster-as-hitter-while-on-rehab-assignment.html