Is it permissible to import a lot of meshes in one FBX to Unity

Hi! I’ve sent my 3d pack on submission on the 5th of July. While checking my pack using Asset Store Tool there was found a YELLOW marker warning that each mesh has to have corresponding prefab. Well, maybe I understood this rule wrong before. I’ve imported each building as one FBX with a lot of meshes inside and created one prefab to it. Is it permissible to do so, or should I rebuild the pack from a very beginning and import each mesh as separate FBX and create prefabs to each of them and build buildings again? Submission queue takes to long and I start to think it’s because of that warning
Thank you