Its common for FWB to get some backlash.. FWB's like lots of labels have full range of meanings.
.From friends that simply fuck without commitment or even honesty (aka the booty call) which likely relates more to swinging.
.Or Friends that you love sharing intimate time with you, like your lovers.
So it can be poly and can be excluded from poly. Just depends on how you view FWB's. But no, it is not a synonym. They can overlap in meaning.. but not always
For the record, I really dislike the term evolved polyamory. haha.. it wigs me out since it makes poly sound like something occurring as a logical progression to monogamy. Which I don't believe it is. Its a whole different staircase, not a better one haha..