This is true. A Bridge Too Far both includes incidents that actually happened but were deemed unrealistic by critics, as well as omits certain details specifically because they would be assumed to be unrealistic.

The one movie I would love to see is one about the battle for Castle Itter toward the end of the war, where Americans, German soldiers who had defected to the resistance, a deserting SS officer, and a group of prisoners including two former French prime ministers, two French generals, Charles de Gaulle’s sister, and a pre-war French tennis champion all teamed up against an SS force attempting to recapture the castle and the VIP prisoners within. Which sounds like a completely absurd movie but it actually happened.