When I look at your link it doesn't seem to be the case that this is about laws enabling gay marriage. It's about a law called the Oregon Equality Act of 2007 that prevent businesses to discriminate against gay people. Whether or not the government has a law recognizing gay marriage that law would prevent bakers who fall under the "Public accommodations" section from baking those cakes. Given that only in 2014 Oregon seems to have returned to legalized same-sex marriage. That gives 7 years without a government having legalized same-sex marriage where as far as my understanding goes a baker should be banned to refuse selling wedding cakes to gay couples.

I agree that the laws in question are different, I would argue that the passing of those laws aren't independent events.

Apart from that I don't think it makes sense to have special regulation about baking cakes that specifically speak about the freedom of bakers to choose whether or not to bake cakes for certain purposes.

Except that's just what we have here. If say the KKK asks for a cake that depicts a black being lynched the baker is likely to refuse and is likely to be able to get away with refusing. What the law, as interpreted in practice, says is that baking a gay wedding cake is something that bakers specifically cannot refuse to do.