No. They really don't need anything that instantaneous. The center of gravity of the rocket is _very_ low. The rocket is basically a bunch of really heavy engines and a couple thin walled propellant tanks. Those tanks are very close to empty at this point (the heavier propellant, kerosene, is in the lower tank).
It's quite stable. The welded shoes are just a 'belt and suspenders' approach.
Engineers are waiting on a vessel a safe distance away in case the landing doesn't go well. Then they go in and weld the feet once the rocket has vented the leftover LOX (Liquid Oxygen). I think they are also attaching guide wires to the top, but i can't confirm that.
