One of the toughest things for leaders to master is kindness. Kindness shares credit and offers enthusiastic praise for others' work. It's a balancing act between being genuinely kind and not looking weak.
There is no upside to making a disparaging remark about a colleague. If your remark is accurate, everybody already knows it, so there's no need to point it out. If your remark is inaccurate, you're the one who ends up looking like a jerk.