Plausible deniability?
It is not like the have to buy their own shares back, so realistically the money is not lost. They would have to make it look good, and buying shares on the way down is a decent way to do that.
Like I said, I am not saying that I believe this (and realistically, I don't believe a word of it), I am just playing devil's advocate and saying that I can see possible motive.