As revealed by Dharmesh Sheth, Zion Suzuki did not actually turn down  Manchester United , but he just felt it was too early to make the move. British journalist said:

” Zion Suzuki is someone they looked at, and there was an agreed-upon deal.”

 Suzuki did not land at Old Trafford. 

I think it’s a bit unfair to say that Suzuki turned down Man United. I think, at this stage of his career, Suzuki may think this move has come too soon for him, because Suzuki needs to. thinking about next year. Japan will be participating in the Olympic Games, and Suzuki wants to be part of their squad.”

“Perhaps, he thinks that a move to Man United will not lead to a regular start in the first team. So while still with the Urawa Reds, the loan deal is between Suzuki and a club. The set from Belgium Sint-Truidense is almost complete, from the information we have.”

“I think Suzuki will often be starting in the first team with Sint-Truidense, so that’s the situation.”