Meaning of xPub in SegWit wallet on blockchain.com and their legacy-type addresses

Question

According to my understanding, an xPub of a Legacy sub-wallet should begin with xpub... and of a SegWit sub-wallet with zpub.... And the addresses begin with 1 and bc1 respectively. But on blockchain.com (where I only have one wallet) for the SegWit sub-wallet I get an xPub beginning with xpub... instead of ypub.... And the addresses generated with this also begin with 1.

When exporting the xPub from Electrum native-SegWit sub-wallet with the same xPrv, I get an xPub beginning with zpub..., as expected.

Is there a purpose on providing the xPub for a SegWit sub-wallet instead of the zPub? Addresses created with the xPub don't show up neither on blockchain.com nor in Electrum.

After being curious about this, I used both xPubs on blockchain.com xpub explorer (https://www.blockchain.com/de/explorer/assets/btc/xpub/xpub6CM...) and found all transactions on the corresponding addresses. As expected, older ones on Legacy addresses, newer ones on SegWit addresses.

And to my surprise, with the xPub of the SegWit sub-wallet I also found an address with balance on it within the addresses beginning with 1. This address doesn't show up neither on blockchain.com nor in Electrum(Legacy & native-SegWig). But it is also found with this tool (https://blockpath.com/wallets/local/101?action=appxpub) with index m/0/2.

In addition to my first question, how is it possible to get access to this address?

Answer 1

To answer your first question: The format of the extended public key defines what kind of addresses are created from it. In other words xPub... and zPub... are both versions of the same key but zPub... additionally instructs the wallet to derive a segwit address from it. But blockchain.com does not use this standard and instead encodes it with xPub... standard.

You can use this open source tool to convert your extended public key to the other versions https://jlopp.github.io/xpub-converter/ if you want to see that the yPub... in Electrum matches your segwit xPub...

And to answer your second question: You can try to access the mystery address of your blockchain.com segwit wallet by using extended private key (xprv) of the segwit wallet and setting the derivation path to m/0'/0'/n' or m/44'/0'/n'.