I mostly agree, but I think there's some slack in the semi-fasts timetables. Pre-Covid when I did that return leg to Leeds daily, we'd pause at Barnsley most days, and Kirkgate. Leeds, we'd sometimes arrive early and have to wait for the semi-fast to depart so we could take its place on P17. Plus, that crawl after Horbury Junction towards Kirkgate.
Interestingly: 0804 Leeds to Sheffield (NT) arrives 0904 (60 minutes); the 0811 XC arrives 0854 (43). On the way back, the 1718 NT arrives 1813 (55), the 1721 XC arrives 1802 (41). It's slightly quicker heading north by either route, which I'm guessing is down to the need to flight everything approaching from the north of Sheffield.
I'd rather hoped the faster via Westgate service would be running by now - I guess it's down to pathing, which another difficulty in truncating and redirecting the Huddersfield service to Westgate.