It is not necessary as this is a virtual fork as opposed to a hard fork.  Now, hypothetically speaking, if BTX were to fork down the line, resulting in a new currency, then it would be best and high advisable that the new blockchain with the resulting new currency have relay protection as this new blockchain would be identical to the legacy BTX blockchain.  It wouldn't be necessary that the legacy/incumbent blockchain have relay protection as the new block chain is a copy of it and not vice versa.