The FMS is of little value in assessing wind for landing (background or trend info maybe); see page 15 of the report -
“Safety aspects of tailwind operations”.
Also, note that although the reported tower wind is more accurate than the FMS it is subject to some significant error, which could place the aircraft outside of the tail or crosswind operating limit. See the report
“Safety aspects of aircraft operations in crosswind”.
“
… that a reasonable probability does exist, that while wind reports to the pilot do indicate that crosswind is not exceeding 15 Kt, in reality the actual encountered crosswind during the landing phase can deviate 10 Kt or even more from the reported wind.
For even higher reported crosswinds, deviations may increase accordingly.”
Tailwind reports could have similar errors.