Even before DC, I have had to delay International shipments because I didn't have the customer's phone number. AND I had a note in all of my listings explaining that I require it for International customers. For my last International sale before DC, I emailed the customer daily for 5 days before she responded with a phone number. I now have it in all CAPS in every listing, so maybe they'll read it now. And I state I need "a" phone number, not "your" phone number, so they can give me any number they'd like. I will not put my own out there, I get enough spam/telemarketers/bot calls as it is.
I agree with everyone that this info needs to be captured and provided to us for every international DC sale.
DEAR ETSY DC TEAM
It's one more field. Please add it to the DC form. An easy compare piece of code will determine whether the Telephone Number field is required if the customer's country is different than the Shop's country.