extra-intestinal manifestations are not remission. even if the bowel is tame a collection of EIMs means there is something active at a histological or subclinical way.
The whole IBS with IBD thing is interesting and a bit debated among gasteroenterologists and the literature. Is it really inflammation-free IBS, or just undetectable IBD Inflammation causing it? I won't go as far to comment on extra intestinal stuff though. An interesting thought and maybe related, I dunno.
Right now, it's common for our gasteroenterologist to say there's nothing they can do when our labs are normal, and shrug the rest off as merely being IBS. Anything absent inflammation is considered to be an IBS problem. IBS does have anti-diarrhea meds for IBS-D and dietary changes that could help.
There's also physical changes that can cause some of it. If you have a history of rectal inflammation then you can develop what's known as "lead-pipe sign" in an x-ray. Your rectum looks thick walled from scar tissue and straight just like a lead pipe, with a total loss of normal haustral folds. A normal rectum has thin walls and is very lumpy and bumpy in appearance (that's the normal haustral folds). Scars from inflammation cause that change.
Impact? Thick walls impact normal rectal muscle movement (motility), causing muscle spasming (that is diarrhea) or incomplete muscle motions (that is constipation). So that sounds a lot like an IBS presentation, right? Scar buildup within the sigmoid colon can also impact constipation/diarrhea presentation as well.