+21 isn't allocated, but

   +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)

Doesnt this defeat the purpose tho as it could be filtered?

The us government monitored all DC residents personal communication for over 2 years because they fat fingered the collection regex. The country code for Egypt is +20, the DC area code is 202.

You think that was a mistake, huh?

That is a mistake that sounds suspiciously self serving, given how many powerful people live and work there

Yes, this data could be quickly mitigated.