Permitting sharing of personal contact info could be misconstrued in certain contexts as promoting it, and that could in turn generate liability for a website.
I can understand the website surveillance watching out for this and not allowing it. What I don’t care for is that you don’t know which members are potentially tasked with administrative oversight of private communication infractions. I once used the word “number” in a private message regarding speaker drivers, and the software interpreted in a way that put the whole convo “under review” as a possible violation, tattooed in red font from that point forward. Eew.
Point being, while their system probably won’t change such an overarching policy, it could still stand some technical improvements for operation within said design. 😁