There's a lot of misinformation about Kane tbh.
His Orient loan was his first ever loan he got 5 goals in 18 appearances most off the bench and out of position. He won young player of the year at Millwall on his second loan scoring 7 goals in 14 games. He was also involved in all England youth levels, and at one point had scored 10 goals in 12 games for the U21s.
His 'bad loan looked awful at youth level' comes from his time at Norwich and Leicester. At Norwich he made 5 appearances off the bench and then broke his foot and had to return to the club. At Leicester Nigel Pearson only gave him any game time on the left wing where he looked awful, he spent most of his time warming the bench with Vardy who also couldn't get in his team.
Before his breakthrough season (also Pochettinos first season) our most famous youth team watcher WindyCOYS predicted he would be our top scorer that season before the first Premier League game had even been played. He was also a goal machine at club U21 level.
edit: Sorry about the rant was only visiting this thread because I was interested what was being said about his amazing performance today.