From what I can see, he echo'd a commented line of code. Essentially wasting some bits in a transmission. I would be astonished if that was actually able to cause a failure

I've seen this mentioned elsewhere in this thread, and it's incorrect. You're unfairly bashing the parent while not really understanding the scope of potential complications. That said, I do want to emphasize that an echo command is generally (like, always) considered to be a safe operation. However, it is not a source code comment (always safe). It's perfectly reasonable for the parent to be nervous about sending unnecessary commands to a rover on Mars, even if I wouldn't personally lose too much sleep over it.

To elaborate :

Source code comments are 100% safe. 99.99999999999% if you want to allow for the possibility of some super duper extra esoteric compiler bug. This is because they are disregarded entirely by the compiler by, for instance, by being treated as whitespace. Nobody audits source code comments for vulns, because that's not, like, a thing. They are safe as can possibly be.

Command arguments, on the other hand, are not innately safe, because they are directly evaluated by the compiler. They occupy space in memory, and even small deviations from an expected value can cause serious bugs. Any time you pass an argument to a function, you know the CPU is - at one point or another - examining the 1's and 0's that correspond to said value. In addition, you also know that those same values will occupy space on the stack, pass through the CPU registers, possibly be assigned to the heap, etc. In the abstract, command arguments have the potential to be incredibly dangerous. For illustration, errors resulting from improper handling and sanitization of inputs are at the root of a massive number of real world bugs-slash-exploits (SQL injection, buffer overflows, etc.).