As a beginner at this game, I must say that I constantly hear instructions that would be utterly incomprehensible if I didn't know what they were saying! It's like those recordings played backwards that some people believe contain a message about devil worship, the imagined message becomes audible only when someone tells you what it says. Indeed, the advice on 'understanding ATC' usually says know what to expect. But isn't that a bit of a problem?! Isn't there a constant risk of expectation bias ? a good example is when I ask for a frequency change, I know what freq I will be given, indeed I invariably have it pre-set on the radio, but even then all I hear is 'callsign bleeegh', I cheerfully read-back the freq I expected and switch over. Similarly, it took a while for me to learn that the noise I hear from ground after landing says 'baseviabravo'. I guess I can always extract the critical things like clear to take off or land, line-up and wait etc and there are things I know I cannot do until I have actually heard a message, but it seems to me that 80% of the comms from ATC are a sort of token noise on which pilots impose the message they expect!