From
https://www.faa.gov/air_traffic/publ...ection_13.html (emphasis mine)
Ground stop(s) (
GS) override all other traffic management initiatives. Aircraft must not be released from a
GS without the approval of the originator of the
GS.
- GENERAL
The
GS is a process that requires
aircraft that meet a specific criteria to remain on the ground. The criteria may be airport specific, airspace specific, or equipment specific; for example, all departures to San Francisco, or all departures entering Yorktown sector, or all Category I and II aircraft going to Charlotte.
The term "stop" may be deceiving, but it's not as absolute as it sounds.
Edit to add: Since you mention the ground stop ended at 4:30 ET I assume it was this one:
https://www.fly.faa.gov/adv/adv_othe...eDate=11/29/22
DEP FACILITIES INCLUDED: (Manual) ZLA ZAU ZLC ZDC ZNY ZFW ZOB ZDV ZOA
ZSE ZBW ZKC ZME ZID ZAB ZMP CYHZ CYOW CYUL CYYZ CYQB CYTZ CYYC CYEG
CYLW CYYJ CYVR