14 CFR Part 101, Subpart D – Unmanned Free Balloons excludes PicoBalloons due to their size and form

That would explain the difference in experiences. My balloon was 8' diameter at launch and expanded to ~40' when it burst at ~90k'. Mine needed the radar reflector and blinky lights. They were supposed to blink at a certain rate, but we cheated and had lights blinking faster as that's all we could find for our budget/schedule.