Doubt it, but maybe a bit of TRT. That is a good bit of size to put on in 10 months but not completely impossible. Especially if he's taking creatine, (I know, I know, the joke writes itself). If he is supplementing creatine though he could be having an excellent response to it and 5-10 lbs of that could be pure water weight. Creatine actually allows muscle cells to suck up a bunch of water and can make muscles look more pumped. It's not like when you naturally retain water and just look fatter. Could be TRT though too. Idk how hard it is to get a prescription where you are but it's a cake walk in the US. I just got back into lifting over the last year and started really fat. I got my T checked and it was deff a bit low but still "normal". Doc offered it right there. I said no because I was overweight and already worried about heart problems, but I kinda wish I had said yes lol. After recomping and 70lbs of fat loss my levels wen't WAY up and the offer was rescinded...

It really doesn't do much to a lot of people, but I have seen some guys look like they gained some size after taking it. Usually, if it works for you, it puts on between 5-12 extra lbs of water. So he easily could have gained like 10 lbs of actual muscle and another 10is in water making him look like he gained more lean mass than he really did.