> to put URLs in the descriptions [...] Phone number "verification" is nasty
Spam is a huge problem for any large platform with free accounts, and there aren't a lot of good options to prevent it. One set of mitigations is around increasing the cost of an identity. Email addresses are infinite and free, but working phone numbers are limited and usually cost money. So gating spammer-desired activities on phone numbers makes sense from their perspective. They could get a similar effect by requiring a credit card number, but people hate that even more.
If you'd like to work around this, I'd suggest getting another number for just this. Google Voice will give you one for free, and the Burner app will do it for $5/month if you sign up via web. Or in my case, my ISP gives me a free landline number with my internet service, which is great for this sort of thing.