no no... size is size is mass you are correct.
but LEAN size refers only the MUSCLE you have gained, which can be kept btw.
SHEER SIZE is just bigger in general, can be fat, bloat, water weight, muscle,etc.. understand.
gaining lean mass and being ripped is good for physique (in my opinion )
whereas you could bulk , gain a shitload of sheer size but have no difinition and look like the staypuft man and then need to cut it down, understand better ? hope that helps