Fire curtains are tested per the recently introduced (2014) UL 10D standard. To provide the fire barrier separation that is required for atriums, the assemblies would need to pass ASTM E119 or UL 263, which have radiant heat requirements, whereas UL 10D does not. Thus, wall assemblies and some glazing assemblies that can pass this test can be used as fire barriers.
However, since the fire curtains currently on the market probably could not pass the ASTM E119/UL 263 heat radiant portion of those standards, they are tested using UL 10D. Therefore, fire curtains cannot be used as a substitution for the fire-resistant fire barrier--they can only be used as fire-protected openings.
The 2021 IBC is the first IBC edition to include the UL 10D standard. Section 716.4 only permits fire curtains to be used to protect openings for smoke and draft control assemblies. If you are subject to an earlier edition of the IBC (which is my case), the use of a fire curtain would have to be approved via a code modification per IBC Section 104.11.