Simple and predictable, which is both its virtue and its flaw.
The weakness: predictability is exploitable. A counterparty who detects a mechanical schedule can trade ahead of the remaining slices. Real implementations randomise timing and size for exactly this reason.
Versus VWAP: TWAP ignores the volume profile, so it trades the same amount in quiet periods as in busy ones - which means it demands a larger share of liquidity precisely when liquidity is thin.