SEA FCO Premium Economy Details

Anybody have a sense about the PE seats for the SEA FCO route? Seat map shows 3-3-3 just like economy and in a shared cabin.

Are these seats the equivalent to the premium economy seats on their 737s for domestic travel? Meaning is it just a little extra legroom and not the type of PE you might see on BA or JAL?

Would love an opiton between being squeezed in Economy and a 4K one-way Business ticket and would like to know what I should expect for the "Premium" ticket.

Thanks.