Yeah, Imprisoned applies a continuous effect that changes Kaito into a colorless land this is applied in layer 4 with a more recent timestamp than Kaito’s ability.

Layers are irrelevant in this situation. It's a time stamp issue with Arena. Judge rulings is that Kaito doesn't become a creature.

Source: L2 judge Peter Davies

And yet another example of the Kudo / Ygra / Ashaya misunderstanding on the player's side. Abilities are lost in layer 6, but all those cards, Kaito included, change card types, which happens in layer 4, so before any abilities are lost, regardless of the relative timestamp order of those effects. Because layer 4 effects always come before layer 6 effects. And per rule 613.6, if there are other parts of the effect that apply in later layers, those parts of the effects will still get applied, even if the abilties creating the effects are removed.

613.6. If an effect should be applied in different layers and/or sublayers, the parts of the effect each
apply in their appropriate ones. If an effect starts to apply in one layer and/or sublayer, it will
continue to be applied to the same set of objects in each other applicable layer and/or sublayer, even
if the ability generating the effect is removed during this process.