Airlines have guidelines for their pilots using OPT (or equivalent) and/or tables to find crosswind component instead of using sine in flight.
An example fo such statement could be:
"To calculate the crosswind component: Enter the table below or OPT with the highest reported wind value (steady wind or gust). Use the angle between wind direction and runway heading to calculate the crosswind component."
Then depending on using this for departure or arrival additional restrictions may be imposed, for example:
"Approach speed correction: Half of the reported steady headwind component plus full gust."
The winglets are not tested by Boeing in same weather conditions as original wing without, possible as discussed due lack of suitable weather conditions during testing.
There is therefore a demonstrated crosswind limit which the manufacturer has published for the original aircraft, while ABP published a maximum for winglets at a later date.
It is up to airline to interpret their guidance on limitations and decide whether to reduce them further for the pilot body to be used.