SIGH
Lean gains are going to be mostly in the form of water gains, THATS how your body grows…and the water gains will be more significant parituclarly when you gain rapidly over a period (suddenly loading carbs or creatine+muscle memory+1st cycle whatever). Its still “lean gains”, and thats what happens when you suddenly blow up fromn either an increased intake or anything else like I mentioned.
Thats why you need to hold your gains a substantial amount of time to gain some “density” or you’ll just piss (literally) these gains away if you take a break or start dieting down right away.
Anyway, if someone gained 8 pounds without significant increase in skinfold, good fucking job.