You didn't use that to get your BLD times, did you?
As for your actual question, clearly it violates the spirit of the following rule:
3h) No modifications are allowed that enhance the basic concept of a puzzle. Some examples of enhancing the basic concept are: new moves are possible, normal moves are impossible, more pieces are visible, colours on the backside of the puzzle are visible, moves are done automatically, more or other solved states.
I'm not sure whether it violates the rule itself (as opposed to the spirit of the rule), though, since the rules don't define what normal moves are, and if the standard Rubik's Clock does those moves, one could try to argue they are normal moves.
I fixed that up, however, if I force it, I can still turn clocks on both sides simultaneously. I guess this could be considered like a corner twist on a 3x3. Not meant to happen, but on an old cube (or DIY) it can. Only problem is that on clocks, every edge permutation is possible, so you can have all but one edge solved. I also have a KO clock, on which this problem happens on every turn, as the pins fall down. So I'd definitely say this is an illegal move.
