It's completely true, it's your comment that's complete bollocks! It's the policy of all airlines to ensure their passengers have the correct documentation to enter the destination country.
The risk to the airline is that Thai Immigration can refuse entry without onward travel within 30 days if arriving visa exempt. Immigration will blame the airline for allowing the passenger to travel without the correct documentation.
The Non Imm O is the marriage visa, you can apply for the 1year extention of stay based on marriage when you have 30 days left on the visa. You'll need 400k Thai Baht seasoned for 2 months in your Thai bank account prior to your application