My understanding of what happened with the electoral reform promise is that the Liberals wanted a specific form of electoral reform: ranked choice. Unsurprising, because as the centrist party, they would stand to benefit most from that system. Which isn't to say I necessarily disagree with it; personally I think a system that encourages moderation is probably a good thing. Anyway, when the committee they put together to study the issue didn't come back with that option, they just shelved the whole thing.