If you’re de-arrested you’re not locked in a cell (custody). If you’re released after questioning it’s being de-arrested.

https://www.bbc.co.uk/news/blogs-magazine-monitor-29784497

“de-arrested” is not technically the same as “released without charge”. The key difference in terminology is whether the person is taken into custody and processed, says a spokesman for the Association of Chief Police Officers (Acpo).

https://www.theguardian.com/world/2006/mar/01/law.emmabrockes

TLDR:

• Arrest - copper has you.
• De-arrest - Copper lets go.
• Released without charge - Released from police custody cell (jail) after an arrest.