Imagine if your fake contact's randomly created email or phone number is on a terror watch list.
+211 South Sudan
+212 Morocco
+213 Algeria
+216 Tunisia
+218 Libya
Someone putting random numbers after +21 because it's unallocated has a fundamental misunderstanding of international phone numbers.But also, the server side is likely to throw away invalid numbers to start with. It's simple and easy to do, and reduces the data storage by a lot (there's a lot of garbage in people's address books)