Some thoughts ..
(a) performance certification work is done for steady wind
(b) an individual airline's level of conservatism, with respect to the certification limits, is a matter for that airline's risk management policies, etc.
(c)
Surface wind is measured at 30 feet. because the observed boundary layer near the ground is not dissimilar to that along the wing in that there is a significant variation near the ground ... the certification relationship has been discussed
previously. The wind at 2000 ft is irrelevant .. it is the variation at low level which bites ...
(d)
I understand that it is the performance that is factored not the wind .. not quite. The AFM charts will apply a 0.50 factor for headwinds and 1.50 for tailwinds. This is done by scaling the chart for the reported wind .. but using half that value for headwinds (and 1.5 for tailwinds) in the chart. One can tell if the chart is factored by looking at the wind component grid .. if there is a noticeably sharp kink in the carpet lines at zero wind (where the factors change) then the wind is factored. This will vary from Standard to Standard implementation .. generally takeoff charts will be factored but landing may not be .. in which case the pilot has to apply whatever operational standard requirement is relevant to the jurisdiction.