I don't think "imagination" should be remotely like seeing.
it's completely different than dreaming or seeing with your real eyes, I would qualify it as a "different sense" if you will.
for me, it's much less detailed unless I focus my imagination on the less detailed part.
The distinction between imagination and seeing is regularly blurred, most commonly in dreams, but also on psychedelics or quasi-psychedelics (e.g. cannabis), and also in altered spiritual states (meditative practices).
The two experiences are different, most of the time, yes, but only "completely 100% different" IMO to aphantasics, or those who are high in aphantasia. I.e. hyperphantasia is a thing, and a normal thing for most people in altered states (and schizophrenia might be seen as involving an extreme form of hyperphantasia intruding where it shouldn't, in some cases).
for me, it's much less detailed unless I focus my imagination on the less detailed part.