If he says Montrose then unless he has some reason for lying that's where he was born. Not Forfar, or Brechin, or anywhere else. If he was lying, you have just about zero chance of finding his parentage.
The article on Montrose in the Statistical Account of Scotland (1790-1) says that there were in the parish
4774 adherents of the Church of Scotland
720 of the Church of England
376 of the Secession, including Antiburghers and Burghers
134 of the Episcopal Church of Scotland
92 of two sects of Independents
40 Anabaptists
20 Bereans of different kinds
10 Unitarians
4 Quakers and
24 persons unconnected with any particular religious Society.
The National Records of Scotland has records from before 1800 of two of the Secession churches
(a) First United Associate congregation, (antiburgher), Mill Street United Presbyterian, St Luke's, United Presbyterian, United Free, C. of S.
(b) Second United Associate congregation, (burgher), John Street, United Presbyterian, Trinity United Free, united with St George's United Free church in 1923
The baptisms from these churches are in the 'Other Churches' section on Scotland's People. What that means is that about one in six of the people on Montrose were adherents of a church whose records are not on Scotland's People, and these records may not even have survived at all.
The writer of the article laments that the Church of Scotland records of baptisms are less complete than they should be: "the inattention of parents, and the backwardness of many to pay the schoolmaster his dues, is a matter of very general complaint throughout Scotland". (It was very often the schoolmaster who acted as Session Clerk.)
Some estimates suggest that as many as a third of all baptisms are missing from the surviving records, and the further back you go, the more are missing. So there is a fair chance that your Thomas Hutchison's baptism record has not survived.
