Neither of those men would have been KJVO.Calvin was not unaware of discrepancies in manuscripts and addressed some of those issues. This article by John Murray speaks to that ;
https://www.the-highway.com/articleNov06.html
In Garnet Howard Milne's, "Has the Bible Been Kept Pure?" he recounts the recognition by the Westminster Divines, as well as Luther and Calvin, that there were copyist errors and such in the apographs. This did not prevent them from believing in the inerrancy of Scripture.