The England Under-21 winger has been used as a second-half sub in both of the Young Lions' matches so far - a 1-1 draw with Spain and 0-0 with Ukraine.
Sinclair, who hit 27 goals for Swansea this season, said: "I spoke to the gaffer after the first game and had little words and point of views. He's the type of manager you can talk to, express opinions to and get views across to.
"I didn't speak to him about any other player - we're all friends in the squad. I just spoke about my own situation.
"The gaffer tells you what he thinks and he explained things to me. It gave me a better understanding.
"He had his reasons and has given me his points of view. It is hard to question him because he's the gaffer.
"He picks the team and all I can do is work 100 per cent in training and hopefully get the shout."