No idea why the distinction but the relationship manager I spoke with insisted it's an intentional choice to maintain two separate card products.
In Canada, the Government's Code of Conduct for Credit and Debit Cards requires that card issuers offer a choice. You will find almost every single top-tier card (Visa Infinite or Mastercard World or World Elite) has a lower level version of itself. This is why you'll find CIBC has an Aerogold Visa and an Aerogold Visa Infinite that are virtually identical. Same with RBC's Avion Platinum Visa and Avion Visa Infinite. Same with Capital One's Aspire range, and so on and so on.
There are a few exceptions but those exceptions mostly deal with cards that existed before the Code of Conduct came into force.
The idea is that the banks cannot force a premium card on a customer who does not want that premium card. So, if the Card Issuer wants to upgrade their product to World (and thus bring in much higher interchange fees from merchants) they must also offer an alternative to existing cardholders who do not want the premium product.
Much ado about nothing I'm afraid. The rewards have been slightly improved, though taking into account the fact that they've withdrawn the 25% bonus points after $10k for 2013, I'm not sure it's much of an improvement at all. The insurance doesn't seem to have changed any. That they've maintained a 2.5% forex fee when other Canadian cards have slowly begun doing away with that is disappointing. The ability to transfer points to SQ, BA and CX is a nice perk, but the fact that these transfers are not at 1:1 (BA is 10k points to 8k miles; SQ and CX are 10k points to 9k miles) makes HSBC look cheap. At least there's no annual fee.
The foreign transaction fee could be considered as largely mitigated by the 2% reward they offer for all foreign currency transactions (doesn't matter if it's online apparently). Better than nothing I suppose but it'd be nice if it can waive that fee like the US HSBC Premier card.