It's exactly what you said in your first post.
Non OEM filters don't have the return valve. Therefore on cold starts you may hear lifter chatter and the red oil pressure light may stay on for 3-5 seconds as the oil circulates. I've experimented with this on mine. Same engine as you, IS300, 2JZ-GE. With OEM filter, no chatter, no red oil light. Non OEM filter, 2-5 seconds of chatter and oil pressure light on start up