German occupation policy during the war grew out of a mix of historical and current political realities, military needs, and a generous dollop of Nazi racial policies slathered over top.
For Poland specifically, the border between Poland and Germany is a troublesome one, in that the political entities that would come to make up each of those two states had influence in that area in different times, and settlement of the area was split between the two, so that you had pockets of Poles, pocket of Germans, and areas where the two intermingled.
Ever since the Partitions of Poland in the 18th century (when Poland was wiped off the map and Prussia gained control of large portions of it), large swathes of territory belonging to the ex-Polish state and inhabited by many Poles were German-controlled. Following the First World War, those territories were taken from Germany by the Allies and given to a recreated Poland. German nationalists, naturally, viewed those territories as German, regardless of the population in any given part of it.
When Poland was partitioned again between Nazi Germany and the Soviet Union in September 1939, this history was the key factor informing how the country was dismembered once more. The first part of your question is simple: large portions of Poland are shown as annexed because they were in fact outright annexed. That is, they were formally incorporated into the Reich as innately German, due to the history of German rule over that region and the presence of many ethnic Germans. Teams of Nazi officials scoured the population of the annexed areas to determine who amongst them were German, or possessed German characteristics (which indicated German ancestry and thus meant that they could be "saved" from the perceived degeneracies of Catholicism and Slavdom; this is a fascinating process of pseudoscience and bureaucracy and deserves its own post).
Those that failed the test were forcibly deported to what was labelled the General Government. This was not considered Poland, though it did comprise those territories that were unquestionably Polish in area and population--not even the Reich's expanded views of Greater Germany encompassed this land. The reason I say it was not seen as Poland is because Hitler had no desire for Poland to ever again exist as an independent state (this attitude mirrors the agreement the powers that partitioned Poland in the 18th century signed). The Poles would only exist as a servant race, with all traces of Polish culture eradicated and only the minimal education required to do the work Germans required. During the war the General Government was run directly by Germany, based in Kraków: there was no puppet Polish government.
This is in contrast to, say, the French situation. Hitler had no intention of eradicating France as a political entity. Annexations took place there as well, with Alsace and Lorraine being returned to Germany, but it was left as a nominally independent state with its own quasi-independent leadership, albeit with close German supervision, reflecting German plans for the postwar order. The zone of occupation that covered the north and the coast was a military-administered zone, reflecting the need for continued combat operations against Britain; there was no plan to make that German territory. France would be a weak puppet if the Germans had won, but it would still be France. Poland on the other hand would be gone.
Cheers.
The main reason Poland is seen as a part of Nazi Germany is because the German goverment considered the territory of Poland to be a part of Germany, whereas they didn't officially consider the territory of France to be a part of Germany.
Specifically the Second Armistice at Compiegne between Germany and France stated that Alsace Lorraine would go back to Germany,and in your map Alsace Lorraine is shown as a part of Germany. North France would be under German military occupation for the duration of the war, and there is no reason to think Germany would have officially annexed Northern France even if Germany had won the war.
One difference between the way Northern France and Poland were administered is that while Northern France was subject to German military occupation and German military law, civilian law (things like contract law, regulations for businesses) in France was chosen by the goverment of Vichy France, and was seperate from the civil law in Germany. Whereas civilian law in Poland was the same as civilian law in Germany. Especially in parts of Western Poland that was outside of the General Government, such as the Reich District of Danzig, or the Reich Distric of the Warta river. Laws in the General Governorate were slightly different, however these laws were openly dictated by the German goverment and there was no attempt to make it seem like Poland had its own independant goverment.
Also it should be mentioned that not all of Poland is shown as a part of Germany in your map. Parts of Eastern Poland that were originally annexed by the soviet union are shown as a part of Ostland, and Ukraine.
