It is different for simulated blurriness, because simulated blurriness can’t be modulated by your ocular muscles, so they won’t reflexively strain to focus.

You couldn’t really achieve that effect by actually putting any kind of lens in front of your eyes though. That is not a simulation of blurriness, it is actual blurriness.

This is the correct answer. It’s like using an image with depth to work your depth perception: it won’t work because you can’t transition between each layer to bring them into focus. Seamen who stay in submarines for extended periods are prohibited from driving for quite a while when they get back on land because a submarine is too small of an enclosed space and your depth perception crumbles over time when it’s not being used.

Turning your world into a blur will basically cause your eyes to try and hyper focus at all times, unable to do so. This will lead to massive eye strain but also a ton of headaches and other ailments. It is the opposite of relaxation for your body.