If you ever cross the border from Frankfurt/Oder, the first thing you see in Poland is a giant Amazon building. Despite that building being there, Polish people still can't order at Amazon.
That is not true. Amazon.de is even available in Polish, with free shipping for €39+ orders.
But yes, I think it's likely that an order from amazon.de goes trough Frankfurt am Oder, as it probably originated from one of many Amazon warehouses in Poland.
Before COVID there were rumors that Amazon may officially enter Polish market this year with state-owned Polish Post as the local shipping partner.