I agree with you in general regarding the importance of historical accuracy in film not outweighing the storytelling and overall message, it's just that in this specific case it was rather ironic in that the understandable criticisms Lee (and others) were leveling at Green Book, and that Lee was willing to try and walk out of the Oscars over (apart from wanting to win himself), could also apply to his film.(Not a rebuttal but an observation)
I did my MA thesis on historical feature films and the issue of accuracy was a central discussion point. Short version: accuracy always comes second to drama/storytelling structure (no surprise); inaccuracies are not inherent disqualifiers in terms of the validity of the overall historical points/arguments made by a film (raised some eyebrows on my committee but my oral defence was persuasive); sometimes a less accurate film account is more effective than a “completely accurate” one (film or other format) at presenting an historical truth (also raised some hackles at the defence).
Historical feature films should make an effort at avoiding gross distortions (though on occasion such distortions can be effective) but accuracy should not be the first criterion used to judge such productions. Film provides an opportunity to supplement more traditional sources of historical knowledge that should not be cavalierly dismissed over accuracy. Even bad historical feature films (bad as history) can provide valuable teaching moments.
At some point I’ll see these two films (I occasionally teach post-Reconstruction US survey courses) and see if they can be useful.