Confusion on Co-Ownership under TPA: What's the Big Deal?

Bhai, I'm seriously stuck on this. In section 27 of Transfer of Property Act, 1882, it's stated that a co-owner can't sell even one share of property without the consent of all co-owners. But what about the proviso? Doesn't it say something about an absolute necessity to sell one's share? So, how does this proviso fit in with the main clause? Abhi toh I'm thinking, either the main clause is redundant or the proviso is superfluous. But when you think about it, what if a co-owner really needs to sell their share for medical reasons or something? Won't the main clause block that? Some professors say it's a mere technicality, others say it's a vital clause. Kaha hai sach?