Of course he'll learn, he's been completely clueless defensively. He hardly even has a claim at being better defensively than O'Connor or Laird. He learns from every game at any level.
He played 6 games for Porto. You may as well try claim Angel Gomes is from our first team. McTominay has played more first team football and even he dropped back down for a game the other week.
He'll be playing with Angel, Chong, Mason, Jimmy Garner and others who train with the first team almost every day so what a shit point.
He's spent months on the sidelines playing like once a month where he could have got additional games in the reserves. Instead now he comes out of the cold for his first start every month and is consistently beat by the most basic movement on the outside.