The legal explanation clearly states it is applicable to highways only. I'm sure 25mph / 40kmh is not the intended way of driving there.

So yeah, I still don't believe you that I'd be fined for driving 25mph in an area, where 25mph is the speed limit.

“unless the reduced speed is necessary for safe operation”

If somehow you got a ticket for this, you’d just say it was necessary for safe operation, after all, why else would there be a speed limit in the first place?