When I use the “Push to repository” task to save values and store the result ID into a local variable, I have it in the format ‘[ID]’. The resulting variable is not usable for further lookups without a manipulation.
I can’t answer with certainty but my guess is that since arrays in Javascript are between square brackets and that the Connect Solution is based on Web language (HTML, CSS, Javascript, etc…), it was choosen for that reason…again, this is my guess.