The picture from
this tweet makes it appear that they are more like supports (and they are called such in the annotations), rather than actual clamps:
In general "clamps" provide a rocket some or all of:
--Supporting the gravitational load of the launcher when verticalized. This seems to be the case with Starship.
--Resisting tipping (lateral load) while verticalized, primarily due to wind. This is likely the case with Starship. Its a big rocket, as it were.
--Providing resistance against launch thrust for early motor operations. While not represented as such, IMO this is likely the case with starship. Basically, the motors need to come up to some nominal flow state/thrust before the vehicle is released, and its hard to imagine all of the motors at that point won't produce enough thrust to offset the gravitational load.
As far as sequencing, the good news is that it doesn't need to be THAT precise, at least in so far as being a more difficult technical lift than any other sequencing that's going on. The ~zero velocity and acceleration in the 'long instant' means any fractional timing offset is pretty much hit with a numerator of "0" and easily overcome-able by normal flight controls. Obviously a properly hung up clamp would be a Bad Deal, but that's both unlikely and another story...
Related, its also plausible they early-release some of the clamps such that the result is a KISS number of clamps actually required to hold back the rocket.
Its also likely that the thrust of the launcher can actually move/lift the clamps in an anomaly scenario. If there are solids involved this is basically a certainty; with liquid motors one could at least imagine a scenario where an anomaly might result in shutting down the motors instead...though methinks you'd still want that feature.