Hello,
As a seller i use the same buyer requirement as well due to the large no. of hit and run buyers (bid, win and never return) on eBay India.
I was however not aware of the fact that 2 eBay IDs cannot share a mobile no. for verification.
Anyways most reasonable sellers would have applied this SMS Verification requirement to buyers with feedback score "0" or lower (eBay gives an option upto "5" or lower) so once most probably once you get a feedback score of 1 (or in worst case scenario 6) you will no longer have to contact the seller.
PS: On an unrelated note, even in spite of having this block in place one of my items was just won by a 0 feedback member with wrong contact no. - don't know how me managed to do that ?:|
PPS: When you are blocked due to buyer requirements, do you see an eBay message clearly explaining why you've been blocked or just some generic message?