Yes, February 2018 against Macclesfield was the last occasion (4-1 defeat....).
I can't remember a 1st v 2nd game this late in the season in the Football League in my supporting lifetime. In 2005 we played Hull when they were second and we were third in League One; in the mid nineties we played Bolton on the Easter Weekend in the Championship, when we both had a realistic chance of winning the league, but neither side was top; in our last automatic promotion season (88-89), we played Scunthorpe at Prenton Park in March when both teams were in the automatic promotion places.
However, I don't think I have seen a first v second encounter.