Drill to utilt and repeat is not an inescapable combo, at least except on maybe a FEW characters. Drill to uptilt IS an inescapable if timed right, and if you utilt spam a bit you might give more damage [character dependant]. Different moves after the drill require different percentages, for example my favorite, dsmash, requires at least 50% on Pit, and requires more to be almost 100% accurate.
Basically, the game cheats by giving more hitstun with more percentage, and as the drill has no knockback...see what I mean? At higher percentages, depending if you hit right, they are stunned longer, and you can do laggier and laggier moves and hit. USmash requires AT LEAST 100% and is horribly inaccurate punishable if I miss that I formed a habit of DSmashing to kill.