(blue arrow) the search that I expected - limited to German because the word I selected was in German.
As you noted, you can override the default behaviour to only find results in one particular language.
I would suspect this also causes the wrong stemming results further corrupting the results.
It doesn't.
Good to know Bradley.
Off topic:
This shows the need of an Analytical Lexicon for German in Logos: you are looking for a verb in imperative (or subjunctive): "der König sage" is roughly translatable as "the king may say" and 'sage' thus is a form of the verb "sagen - to say, to tell" and related to, but not identical with the noun "die Sage - the legend, myth, tale" and the search hit is only coincidental, since this verb form just looks like the lexical, nominative singular form of the noun (save capitalization).
Such an Analytical Lexicon would help to look up thing in the exisiting Geman Theological Dictionary in Logos (here coming up in the search since "sage" is a part of the string "sagen" , most often you would find third person past tense which is "sagte", "sagten" - said - and which is not found in the MTG dictionary
Good to know. This is the sort of detail that I like to uncover so that those affected by it can push for the appropriate resources/changes.