On a lot of shows, when the kids graduate high school, there is some sort of plot device to allow them to remain home instead of going away to school. (On Family Ties, for instance, Alex P Keaton wanted to go to Princeton but instead went to a local school as a commuter student.) So it’s kind of nice that they sent Haley off to a residential college.
Yeah, it might have nothing at all to do with the actress’ medical issues and is just the story the showrunners want to tell. Now they have a new remote location they can send all of their characters off to for an episode or two.
She’s only been at college for 2 episodes, and wherever she’s going is only a few hour drive away (no cite other than they moved her in in a single day trip). They’ll find plenty of ways to work her into episodes - parents’ day at college, Mitch & Cam come up to visit, holidays, first trip home where she brings tons of laundry then disappears for the weekend, etc.
Pregnancy in sitcoms drives me up a wall. Lucy did it over 50 years ago and they all try to copy it without nearly the same success. I think this show didn’t need it. But I do like the way they use it to play up the rivalry between Claire and Gloria.