That's interesting. Never heard of it. If this were policy, every PDX to SEA flight would violate this policy, both on Horizon and the mainline flights. No free local craft beer or wine. (Of course, they usually use turbulence as an excuse to cut out free alcohol service on this route. But usually (both on Alaska and American), on longer routes, they wait to pick up first class drinks until the last possible minute. I don't know for sure, but I suspect the flight attendant was just offering substandard service on your flight. Happens sometimes.