I want to create a new wallet without using the bitcoind wallet.
I have created a testnet wallet on blocktrail.com so I use
pubkeys from blocktrail and from bitcore package (node.js).

pubkey generated by bitcore:    n2eTmd37KTGhRZNJsf9tfVdCG1YejciETu
pubkey generated by blocktrail: 2NCo1Y7JJgLabJ5AQjBpgavyX1JLWJxGPYK

my transaction: from n2e... to 2NC... change back to n2e...

When I do a createrawtransaction I have two different types of scriptPubKey:

n2eTmd37KTGhRZNJsf9tfVdCG1YejciETu:     pubkeyhash  (bitcore)
2NCo1Y7JJgLabJ5AQjBpgavyX1JLWJxGPYK:  scripthash     (blocktrail)

My question: why I have a scripthash from blocktrail ?

What I think the answer is:
quote from blocktrail: "The BlockTrail Payment API is built using Multi-Signature HD Wallets, this means that there are 3 keys in total, 2 of which are necessary to get access to your Bitcoin!" (primary key, backup key and blocktrail key)
so instead of paying to a single pubkey, I must pay to a scripthash representing 2 out of 3 signatures.

Is it correct ? or there is another reason ?