Section 21. This chapter applies to a transfer within the scope of section two made after its effective date if:
(1) the transfer purports to have been made under the Massachusetts Uniform Gifts to Minors Act; or
(2) the instrument by which the transfer purports to have been made uses in substance the designation ''as custodian under the Uniform Gifts to Minors Act'' or ''as custodian under the Uniform Transfers to Minors Act'' of any other state, and the application of this chapter is necessary to validate the transfer.