If you know what to listen for it’s pretty easy to figure it out. Here’s the song on YouTube and the morse code part starts around 2:30. Super cool.
When code was required for US ham radio licenses, it took passing a 20 wpm test to get the top license (Amateur Extra). Commercial Radiotelegraph Licenses used to require 20 wpm for a second class license and 25 wpm for a first class license.
Unless someone was in the equivalent of the Signal Corps, I'd be surprised if they could copy the message.
It wasn't necessary for everyone to be able to decode it themselves:
> one rescued hostage spoke of hearing the Morse code message in his psychological evaluation and had passed on its meaning to his fellow captives.
Among hams, this was not all that strenuous to decode, particularly if the song is repeated.
Many hams, particularly in Europe, work contests at speeds at or over 40 wpm.
I'm one of the ones that got the Extra class license at 20 wpm. My peak speed was about 40 wpm. One of the teachers not far from where I grew up, W7QYA, Flo, was usually found at 60 wpm.
There is a weekly operating activity called CWT from CWops where the speeds are often on the order of 40 wpm.
It sounds like their basic training covered Morse Code. I know that pilots used to be required to know the code.
Some time ago, the requirement for Merchant Marine operators to know code was dropped. Nowadays, it is pretty much ham radio operators that have facility in morse code operation.