In the toilet bag are mentioned: soap, towel, comb, brush, toothbrush, toothpaste, shoe polish, sewing kit, in summer: sunburn cream.
Even taking into account that sexual maturity 80, 90 years ago was later than today due to the nutritional and health situation, it is certainly conceivable that some 17 or 18 year olds with strong hair growth also had a beard fuzz on their upper lip (a few decades later, this was vainly cultivated). In the 30s and 40s, beards were completely out of fashion, so that should have been removed. And of course, shaving was "proof" of adulthood. I'm thinking of the flak helpers around adults, for example - even though there may not yet have been anything to shave...
Some older people may have done it that way, but it was certainly not the rule.
What was required was "freshly washed, well coiffed, short hair, clean fingernails" - and certainly smooth cheeks.