Its pretty standard in most movies for hair styles to reflect the time and place they were made and not the time and place the movie depicts. This particularly true for women and for the primary cast. Extras in the background will often have more accurate clothing and hair. Another example of a movie with the star wearing the appropriate military haircut is The Warlord, (1965). Heston has the 11th C. Norman haircut
To look at the other side--- In movies like "Saving Private Ryan" and many others the Germans are portrayed as having shaved or at very least exceptionally short hair. In reality, look at photographs from WWII. The Germans almost always sport hair noticeably longer than their Allied adversaries. Accounts by GIs often mention the "long, greasy hair" of the Germans. But modern neo-Nazis favor the skinhead look, so we back-project that look onto the Germans of the mid-'40s.
I would say that mainly depended on two factors.
Distance to Hauptkampflinie and progress on time beam.
The closer to HKL and the later in war the less time, emphasis and discipline in respect of proper make-up and outfit.
May the first US troops during 1943 to mid 1944 have met comparably well equipped German front soldiers in good physical condition things tipped to the worse with any new conscription wave.
And already at that time most German troops had not much in common anymore with those of the earlier waves, pre war up to mid 1942 latest.
Once the West-Allied crossed the German border in early 1945 they literally met the very last reserves, scraped together to hold their bones into the fire in a long lost fight.
Supportive troops and staff located more rearward usually looked a bit better, especially those higher ranks.
Though the circumstances in the late western theater have still been way less existential, devastating and grinding for all German troops, compared to the things happening in the east.
All above is of course only just scratching the surface and my very own personal opinion.