The 22-year-old mainly played in a wider attacking role when on loan from Aston Villa last season and in the campaign before.
Grayson has used him more centrally this season and Robinson has blossomed in his time as a permanent signing.
Robinson’s two goals in the 5-0 victory over Bristol City on Tuesday night saw him join Jordan Hugill as PNE’s top scorer with 11 goals.
“Younger players learn their roles and physically they get stronger,” said Grayson.
“It is tough to play as a striker because you can be up against some big meathead centre-halves at times.
“They are trying to kick lumps out you and players have to learn to adapt to that.
“The work we do on the training ground with them is to learn to get into areas and pockets where they can affect the game.
“Also, the work which the lads do in the gym makes them physically stronger.
“Against Bristol City in the week, we earmarked Callum to play as the second striker and we wanted him central to hopefully weigh in with the goals, which he did.
“If we were to move Callum out wide to be the creator, you then want other players to be in the scoring positions.
“Callum is enjoying what he is doing, after being on the bench quite a bit recently, he grasped the opportunity of a start on Tuesday night.
“He has developed well this season and we like working with him.”
Robinson and Hugill are on 10 goals apiece in the league, Robinson having scored in the FA Cup against Arsenal, while Hugill’s other goal came in the League Cup win over Oldham in August.
North End have found goals easier to come by this term, and have netted 59 times in the Championship going into the last six games.
That is compared to the 45 they scored last season.
Said Grayson: “The level of players you have got at the club dictates how you are going to play and the ones we have got this season have helped us to be more attack-minded.
“Our ethic is to be hard to beat but we have players with a bit of X-factor about them.”
Meanwhile, PNE attacker Tom Barkhuizen is shortlisted for the Championship goal of the month award.
His opening goal against Reading, swept in from the edge of the box, has been nominated, and he has goals by QPR’s Joe Newell and Blackburn front man Marvin Emnes to compete with.
Voting is being done via a fans’ poll on skysports.com which closes on Tuesday.