Not at all. S-Pay had only recently launched on the watch in Canada, debit is an option in the US and debit works on phones in Canada. Debit on the watch would have been a natural extension of the service, and is a reasonable expectation. It's not made clear in any advertising that it's credit card only, and I'm only just now beginning to develop my psychic abilities.
And frankly it's just silly since the watch handles the transaction through the phone anyway, on which debit is an option.