Purpose was not to get lean ( he was a lean muscular beast already ), purpose was to get lighter to protect joints.
But yeah, looks so weird, it is going to take us some time to adapt to this new him.
I wonder what will happen to his SLRVJ, he was doing in-game head at rim and FT SLRVJ dunks being 250+, and SL jumping is much more dependent on weight than muscle ( his joints and levers are the same anyway ) so imagine now!!