When almost any block besides fire is broken by hand, a vibration is sent to the sculk sensor and it activates, as per design. However, fire appears to be an exception - breaking a fire block by hand will not create a vibration despite this obviously being the breaking of a block.

Interestingly, breaking the block below fire does in fact cause the fire to out out a vibration as it breaks, which is the expected behaviour (the base block shown in these screenshots was just out of range of the sensors).