Farmers need to feed the stock in the hills. That means taking a load up a steep hill in winter - sometimes hairy at the best of times, given the climate.
Add on trying to do it in low light conditions and the problem's even worse.
Sheep don't live by the clock, but by the light level, and if the first feed they get is at nine thirty, then that can cause premature abortion.
The only alternative is to bring the whole flock into a barn....but if you're dealing with a flock of over a thousand, you need a bloomin' big barn!
Last year, several farmers were injured on the hills in daylight. Can you imagine how many more would suffer broken limbs in the gloaming before full light over the hills at ten o'clock?
So a farmer just adjusts his or her day accordingly to ensure that the things that need to be done during daylight hours are done during those hours. Changing the clock makes no difference at all, as all of this is under the control of the farmer.
Where there might be an effect is if someone is in a job reliant on daylight, but also reliant on external factors (e.g. trains running, planning regulations etc) that didn't align. So for example if clocks were shifted so that the the precious few hours of daylight in winter started at 7am, but planning regulations prevented building works before 9am, then this would be an issue as two hours of usable daylight would be lost.
But this doesn't apply to a farmer whose work patterns are under their own control.