The exif ShutterSpeedValue value is generally about the same as the ExposureTime, though it seems often to give the actual shutter speed instead of the closest “traditional” shutter speed.
I’m noting that this value gets imported into Tropy as something very different from what exiftool reveals. Three examples, two from my iPhone, one from Aon actual camera
| exiftool | Tropy |
|---|---|
| 0.000452999999773276 | 11.108201328564128 |
| 0.0450740000942819 | 4.47156070206103 |
| 0.000803591542067366 | 10.28125 |