... or simply that the LOGO language syntax and choice of commands is confusing? Without formal explanation, how surprising is it really that a child would assume that STOP mean stop?
I'd bet that if LOGO had used RETURN, like many other languages, then the children's reasoning would be likely be more accurate. Or go the other way and make them tell you what this or that brainfuck[1] program does. So, to me, this research says more about LOGO choices than anything.
But STOP does mean stop. Stop executing this subroutine.
If the program were instead (as a set of commands for a person, not a turtle) START WALKING; STOP; START CLAPPING; STOP; ... any child would understand what was intended. It would be more confusing if the first STOP here meant "stop all program execution, never proceed to the next step".
So the problem isn't STOP, it's the fact that there's more program to execute, hidden in the call stack.
I'd bet that if LOGO had used RETURN, like many other languages, then the children's reasoning would be likely be more accurate. Or go the other way and make them tell you what this or that brainfuck[1] program does. So, to me, this research says more about LOGO choices than anything.
[1] https://esolangs.org/wiki/Brainfuck