From Alaska Airlines official website:

“ Check-in & boarding cut-off times
Minimum required check-in with bags
When you check bags on our flights, you must make sure that all of your checked luggage has been received by the airline and a valid boarding pass is received no later than the cut-off times listed below to avoid rebooking on a later flight.

In order to ensure your bags are turned over in time, you’ll need to be in the bag drop line well before the cut-off. Please refer to our
airport guides for recommended arrival times at your departure airport.

International flight - 60 min
Domestic US flights - 50 min
“

There may be a local practice at ZLO that is stricter, but I could not find any published Alaska rule saying ZLO requires a 3-hour advance check-in.

I am checking with ZLO airport and chatting with Alaska Airlines for confirmation/clarification and I will keep you updated.

We have been flying out of ZLO for over 17 years and we have never had any problems.

Ps. I can see everyone getting very drunk in the waiting area for 3 hours. At least the airport will sell more of their expensive sandwiches, snacks, water and alcohol.
Pps. I am sorry to hear about your experience Dhyana.