Short-term (<15minute, repeatable) hush modes are considered a safety feature. They prevent angry homeowners from removing the smoke alarm entirely, a far more dangerous situation than a short term hush.

NFPA 72 recommends a desensitization method for ionization smoke alarms and requires one for smoke alarms installed near a cooking appliance, and several states have followed in codifying this into law. Hush is not required for photoelectric smoke alarms, under the theory that they are less prone to cooking and shower-related false-positives, but this feature is still allowed and they are a common user convenience.

UL 217 allows smoke alarms to be provided with a <15 minute desensitization feature which prevents an alarm from triggering unless obscuration/ft exceeds 4%.

Also... the Nest v2 got an in-app hush feature. My understanding is that V1 had some kind of false-positive issue that triggered a ">4% non-hushable" alarm, though, so this wouldn't have mattered.