I’ve never thought about it before, but I wonder if the convention dates back to the days of starting handles? A right-handed person would need clock-wise rotation to swing a handle.

The timing end is a good way of identifying the front, speaking vehicles again. Number 1 piston isn’t reliable as Jaguar, certainly with the XK anyway, numbered from the back. I found that far too confusing and found it much easier to time it 360 crankshaft degrees out.