Only under very special circumstances and at one time of the year. Claiming you can switch without qualification like this is disingenuous.
Yes you can't change from a cheap high-deductible plan to a platinum gold super plan the second you feel an expensive emergency coming on, that is an important note. But it wasn't the context here. For chronic disease management you do benefit from completely freedom to find your way to a plan you like eventually.
It is still a horribly overpriced system though.