@whale-av Pd has a strict order of operations. It tries to compute each tree until the end. If it recognizes a loop, it starts an internal counter. If that counter hits a certain threshold, Pd stops the computation and displays "Stack overflow" in the console.
[delay] schedules an operation for the next cycle of operations. So the first set of operations will be finished, then the delayed operations start. The stack overflow counter will be reset for this new cycle of operations.
This is the reason why the left example above will stop with a stack overflow message and the right one will go on forever without any error.