I got the same email a few weeks back, it came across as very copy / paste so I’m assuming its a blanket email they are spamming people with.
The issue I’ve found with lots of these RF type sites is that because they invest nothing upfront in you as a composer they have a very ‘nothing ventured nothing gained’ approach. They will happily take on thousands of tracks to pad their library out and if they don’t get you any syncs then they haven’t really lost much in the process.
I’d only really bother doing anything with them if its quick to get tracks into the catalog and the tracks you give them have already been made and used elsewhere. Also don’t sign over lots of tracks in one go, trial them with a few and see if they do anything with them.
In my experience the music libraries that are worth sticking with are the ones that invest in you, whether it be time or money. They will bother to get to know you and your work and it becomes mutually beneficial.