So I could sure be wrong, but weather Japan can attack a German-controlled minor power seems like it comes down to this - Is a controlled minor power part of an Alliance?
Germany and Japan are both part of the Axis Alliance weather they are aligned or not. According to table 4-1 (Alliances) the controlled minors of Republican Spain/CCP/Nationalist Spain/KMT are part of their respective Alliances at the start of the game. If the Commonwealth attacks a dutch territory (while they’re neutral), the other dutch territories revert to German control. Since you cannot declare war on a member of your own Alliance (table 4-2), an Attack is a declaration of war, and it seems to be indicated that Controlled minors are part of the Alliance of the controlling Major Power (without being aligned), That says to me that Japan can’t attack a German-controlled Minor, but maybe I’m missing something that contradicts my interpretation there.
France could certainly attack Poland though if they wanted as long as Poland isn’t a British-controlled minor or British-Aligned at that point, therefore making it not part of the Western Allies “Alliance”.