That's not true. Changing a stock sale plan in any way is considered insider trading. The window has nothing to do with whether it's legal or not. It's only used a risk mitigation and is up to company policy.
I think the point the cma was making is that this trick doesn't involve making changes to (formal) stock-sale plans. The formal plan is to sell regularly, and that remains unchanged, you just cancel it by hand habitually, except when you don't.
I am no lawyer, so I don't know if this is really allowed. My gut instinct is (a) no, it is not allowed and (b) there will always be some more subtle version of the tactic that is allowed.
I am no lawyer, so I don't know if this is really allowed. My gut instinct is (a) no, it is not allowed and (b) there will always be some more subtle version of the tactic that is allowed.