The Sheffield- York main line was NEVER via this route. It the late 70s it was via the old Midland main line - diverging at Manvers, then via Cudworth and Castleford. I think the Pontefract route had speed restrictions due to mining subsidence.
Even then the service was VERY sparse, 3 or 4 trains per day - and there were only 2 intermediate stations between Rotherham and Church Fenton ! [ Moorthorpe was the other one ]
Would be interested to know if the line EVER had a decent service.
Sorry, but Sheffield-York expresses used to go this way!
In 1962, there were expresses from Sheffield Midland to York at 12.06am[Mons only],12.50am,, 9.50am, 11.34am, 12.54pm, 1.36pm. 2.40pm, 6.34pm and 9.41pm; and from Sheffield Victoria to York at 1.41am[Mons only],3.43am [Mons excepted], 8.17am and 6.20pm.
Most of these were Midland services from Bristol/Birmingham- York/Newcastle. The 6.20pm from Victoria was the 11.16am from Bournemouth West to Newcastle, which had come via the old GC line.
There was a corresponding timetable southbound.
Mondays- Fridays Pontefract Baghill had services at:-
12.53am to Darlington;
7.53am local dmu to York;
9.10am to Scarborough Central;
10.43am to Newcastle;
11.40am local dmu to York;
12.24 pm to York;
3.43 & 6.43pm local dmus to York;
7.15pm to Newcastle;
7.22 & 10.33pm to York.
And in the reverse direction:-
8.07 & 9.30am locals to Sheffield Midland;
10.27am to Cardiff General;
10.54am to Bournemouth West;
12.46pm local dmu to Sheffield Midland;
1.22pm & 2.57pm to Bristol Temple Meads;
4.55pm local dmu to Sheffield Midland;
5.51pm to Birmingham New St;
6.4pm [Fridays only] to Penzance and Newquay;
8.13pm local dmu to Sheffield Midland;
9.29pm to Birmingham New St;
10.9pm to Bristol Temple Meads [with sleeping accommodation!];
10.53pm to Swindon.
Try getting a sleeper to Bristol or a through service to Newquay now!!
As you say, they were diverted away later because of mining subsidence problems, then later still the markets of Leeds and Doncaster became more attractive as journey-times were speeded-up. AFAIK, one XC service still goes this way today, though, for route-retention purposes.