Plans were disorganised and undermined by St's other policies. In terms of disorganisation, 1st 5YP was launched in Oct 1928, and yet Plan only published in April 1929.
Stalin purged economic planners and industrial managers, ones who made economy work.
Stalin attacked/terror members of Gosplan, to extent that 3rd 5YP was never finished.
Therefore, for periods during 1st + 3rd 5YPs, Sov Un had planned economy, but no Plan.