Where do Reading Foundational Standards fit in?

Just a bit confused on how the reading foundation standards were introduced in the CCRS. They are not part of the reading strand, come at the end of the ELA/Literacy and aren't really mentioned before have no clear introduction. It's also not clear to me why it starts at RF.2 (what happened to RF.1?) and also why suddenly there are no longer labeled as anchors but just RF.2, RF.3. and RF.4. that to me act like anchors as then they are broken down into level-specific standards for CCRS Level A,B,C. And then where do reading foundational skills fit in on tracking level gains in approved tests? Have they been included in measuring skill gains?