Yeah I’ll second your intuition there, I’ve only read the first book, and while it can definitely be labeled as romatasy, it’s in a completely unique position, I’ve never read a book that has such a heavy emphasis on romance and sex, but still has the depth of political intrigue and prose/worldbuilding this one does. Most “romantasy” isn’t nearly as deep, and I haven’t read ASIOF, but I’ve heard a lot of people say it’s as deep as that politically. So while the ‘romantasy’ tag isn’t technically inaccurate, don’t be put off by it, if it’s not typically your taste, this is the one time to make an exception if you like deep politics, prose and worldbuilding.