First are you talking about Wind forecast with is the averaged wind over 10 minutes or about Wind gusts (rafales in French)?
Do you have a mean to measure locally the wind speed?
And which model do you use in Windy? There are 7 models available in your area and it is better to compare them.
Near the Porquerolles island there is the weather station of Hyères airport (at 11 km). I do not see such big discrepancy about wind that you mention.
Here is the comparison with the Observation vs forecast tool that you can use yourself (select Reported wind and click to a weather station). There are not such big discrepancies about wind these last days with all the available weather models.
In aviation weather apps, they show the temperature at the airport/ aerodrome where there is generally a weather station. They cannot compute real temperature with any weather model.
In Windy you can check the reported temperature at Karstrup airport. It is true that Meteoblue provide a more accurate temp than GFS, ECMWF and even ICON D2.
Click Reported temperature to get the Observation vs forecast feature and last reported temp at this weather station.