India: presidential elections and rejection of vote

Once again, an academic question:

Do we feel that the spirit of the law was followed when Mulayam Singh Yadhav's vote was held to be invalid. After all, it was NOT yet cast, was it?

If a person - while still under oath, can revise his earlier testimony, why is a Voter not able to revise his voting preference before the vote is cast?

If the law is as it is, do we believe that it is reasonable?