e.g. a fruit and veg grower, owing a big windturbine can show this label now, but in the distant future every Irish producer can as soon as the wind share in the grid exceeds 25%.

The wind share of generated electricity in the Irish grid is now around 12% of demand. A share of 25% has to be reached soon as it is an Irish plan to export electricity to England and the continent.

Has the grower who invested in wind competitive advantage? Hardly.
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Advantageous to the implementation of wind would be the matching of consumption aka demand to wind generation. Difficult for the grower because he has to supply live stock to his market clients on a daily basis. So lets take IKEA. MDF and Urea glue production and some packaging. We can’t expect them to halt production if there is a windless day and sent their workers home without pay. but the level of adjustment of their production processes to the present wind production level is important and should be expressed in that label.

Regarding the title. At first it seems confronting but in IMHO the wrong product is selected.
One has to look at the whole life-cycle of the computer. 25% of the electric energy for assembly at the manufactures site is neglectable compared to its total electricity use.
Moreover environmental matters of end of live are much more concerning.

Would I pay more for a computer that use less energy for the same performance? Yes I would.

Should I pay more for a computer that has this label. No, but probably I have to.